Book  is  the  flropertg  of 

California   College   of 


SCHOOL  OF  MEDICINE 
LIBRARY 


Transferred  from 
College  of  Pharmacy  Library 


V.1AI 


CALIFORNIA 


COLLEGE  OF  PttyRMAH 


INORGANIC 

GENERAL,  MEDICAL  AND  PHARMACEUTICAL 

CHEMISTRY 

THEORETICAL    AND    PRACTICAL 

A  TEXT-BOOK  AND   LABORATORY   MANUAL 


CONTAINING 


THEORETICAL,   DESCRIPTIVE,   AND    TECHNOLOGICAL    CHEMISTRY;    CLASS    EXERCISES    IN 
CHEMICAL    EQUATIONS   AND   MATHEMATICS;   AND   PRACTICAL   MANUFAC- 
TURING  PROCESSES   FOR   FIVE   HUNDRED   CHEMICAL   PREP- 
ARATIONS,  WITH   EXPLANATORY   NOTES 


OSCAR    OLDBERG,  Pharm.  D. 

PROFESSOR    OF    PHARMACY,    DIRECTOR    OF    THE    PHARMACEUTICAL    LABORATORIES  AND 
DEAN  OF  THE  FACULTY  OF  THE  SCHOOL  OF   PHARMACY  OF  NORTH- 
WESTERN UNIVERSITY,  CHICAGO 


IN  TWO  VOLUMES 


VOLUME    Il.-ILLUSTRATED 

1900 

CHICAGO   MEDICAL   BOOK    COMPANY 
CHICAGO 


ENTERED  ACCORDING  TO  ACT  OF  CONGRESS,  IN  1900,  AT  THE  OFFICE  OF  THE 
REGISTER  OF  COPYRIGHTS,  LIBRARY  OF  CONGRESS,  BY 

OSCAR  OLDBERG. 


ALL  EIGHTS  KESEKVED. 


o 

'  • 


PREFACE   TO   THE    SECOND    VOLUME. 


The  laws  and  conditions  which  govern  chemical  reactions 
and  their  direction,  velocity  and  relative  approach  to  completion 
have  been  treated  of  in  the  first  volume,  including  the  necessary 
conditions  of  success  in  preparation  work  so  far  as  they  may  be 
indicated  by  general  principles.  The  materials  and  methods 
employed  for  the 'production  of  inorganic  pharmaceutical  prepa- 
rations were  pointed  out  in  a  general  way,  the  subject  of  oxidation 
and  reduction  was  fully  discussed,  and  the  use  of  chemical 
equations  and  stoechiometry  explained  and  exemplified. 

Part  I  of  the  second  volume  discusses  more  fully  the  intelli- 
gent choice  of  methods,  materials  and  apparatus,  and  the  prac- 
tical manipulations  of  actual  laboratory  operations  in  the  produc- 
tion of  inorganic  preparations,  and  Part  II  contains  detailed 
descriptions  of  the  modes  of  preparation  of  five  hundred  inor- 
ganic chemicals.  These  processes  should  be  of  practical  value  to 
pharmacists  and  manufacturing  chemists  as  well  as  to  teachers 
and  students.  Chemical  laboratory  work  in  the  schools  has  in 
the  past  been  almost  exclusively  analytical  work ;  but  the  at  least 
equal  value  and  importance  of  practical  work  in  the  production 
of  chemical  compounds  is  now  fully  recognized. 

OSCAR  OLDBERG. 

School  of  Pharmacy  of  Northwestern  University, 
Chicago,  1900. 


419M 

ill 


CONTENTS 
OF  THE  SECOND  VOLUME. 


PART   I. 

GENERAL  PRINCIPLES  AND  METHODS  APPLICABLE 

IN   THE  PRODUCTION   OF   INORGANIC 

CHEMICAL    PREPARATIONS. 


CHAPTER  I. 

PAGES 

Choice   of   Methods   and   Materials 3-9 

CHAPTER  II. 
Crushing   and    Powdering 10-15 

CHAPTER  III. 
Dry   Chemical    Processes 16-23 

CHAPTER  IV. 

Solution.     Its  Nature,  Causes  and  Effects 24-32 

CHAPTER  V. 
Solvents.      Solubility,    Solutions 33-46 

CHAPTER  VI. 
The  Clarification  of  Liquids.     Strainers,  Presses,  Filtration 47-62 

CHAPTER  VII. 
Evaporation   63-69 

CHAPTER  VIII. 
Distillation   70-77 

CHAPTER  IX. 
Crystals  and  Crystallization 78-87 

CHAPTER  X. 
Crystallization  from  Solutions 88-97 

CHAPTER  XI. 
Dialysis   98-99 

CHAPTER  XII. 
Precipitation 100-116 

CHAPTER  XIII. 
Chemical  Solution.     Wet  Oxidation.     Wet  Gas  Operations 117-127 


VI  TABLE   OF    CONTENTS. 

CHAPTER  XIV. 

PAGES 

Uses  of  Unfinished  Products.  Purification  of  Crude  Chemicals. 
What  to  do  with  Damaged  Products.  Profitable  Chemical 
Work 128-132 

CHAPTER  XV. 

The  Preservation  of  Medicinal  Substances 133-140 

CHAPTER  XVI. 
Solubilities  of  Chemical  Compounds  in  Water  and  in  Alcohol. . . .   141-150 

CHAPTER   XVII. 

The  Densities  of  Solids  and  Liquids.  The  Mohr-Westphal  Bal- 
ance. Hydrometers.  Pycnometers,  etc 151-166 

CHAPTER  XVIII. 
Rules   for    Making   Solutions    of   Any    Given    Strength,    and    for 

Diluting,  Fortifying  and  Mixing 167-178 

CHAPTER  XIX. 

Laboratory  Furniture  and  Apparatus 179-196 

CHAPTER  XX. 
Laboratory   Rules  and   Precautions.     What  to  do  in  Accidents. 

How  to  Clean  Apparatus 197-205 


PART   II. 

LABORATORY  MANUAL  OF  INORGANIC  CHEMICAL 
PREPARATIONS. 


Introductory 209-210 

Weights  and  Measures 21 1 

Water . . .. 212-214 

Acids 215-252 

Other  Preparations . . 253-632 

Tables  633-646 

Index  .  647-655 


ILLUSTRATIONS. 


PAGES 

Iron  Mortars n 

Porcelain    Mortars 12,  13,  37 

Spatulas  12,  13 

Drum    Sieve 14 

Crucibles    17 

Crucible   Tongs 18 

Perforated    Porcelain    Basket    for    Circulatory    Displacement    in 

Chemical   Solution 37 

Weighing  Bottle 42 

Dr.  Rice's  Lysimeter 43 

Buchner  Funnel 47 

Perforated  Discs  for  Funnels 48,  62 

Crop  Funnel 48 

Decantation  Over  a  Greased  Rim 49 

Use  of  the  "Guiding  Rod"  in  Decantation 49 

Casserole  50 

Pipettes    50 

Syphons  51,  52 

Automatic    Filtration    Arrangements 52,  62 

Strainer  and  Stand 53 

Tenaculum ., 53 

Use  of  Small  Straining  Cloth 53 

Witt's   Press 55 

Cylindrical    Press 56 

Mohr's  Press 56 

Corrugated  Filter  Funnel 58 

Perforated  Porcelain  Funnels 58 

Perforated  Platinum  Cone  for  Filters 58 

Paper  Filters 59 

Apparatus  for  Hot  Filtration 60,  6 1 

Filter  Pump 61 

Filtration  with  Pressure 61,  62 

Evaporation    Dishes 67 

Porcelain  Stirrers 68 

Desiccator  69 

Laboratory  Thermometer 73 

Distillation  Apparatus 74 

Liebig's    Condenser 74 

Squibb's  Upright  Condenser 76 

Mitscherlisch's  Condenser 76 

vii 


Vlll  ILLUSTRATIONS. 

PAGES 

Retort,    Tubulated 74 

Glass    Tube    Fittings    for    Connections    in    Distilling   Apparatus 

and  Gas  Apparatus 74 

Thistle  Tube  and  Safety  Tubes 75 

Cork  Borer 75 

Perforated  Rubber  Stoppers 75 

Apparatus   Stands 77 

Crystal  Forms 81,  82,  83,  84 

Crystallizer  of  Glass 93 

How  Small  Crops  of  Crystals  May  Be  Drained 95 

Centrifugator 96 

Dialyser  98 

Tubulated  Precipitation  and  Decantation  Vessel  of  Porcelain....          109 

Precipitation  Jar  of  Glass 109 

Beakers    no 

Precipitation  Flasks,  Erlenmeyer no 

Spritz  Bottles 113 

Kipp's  Apparatus 125 

Gas  Evolution  Apparatus 126.  127 

Wash  Bottles 126,  127 

Woulff  Bottles 126,  127 

Mohr-Westphal   Balance 156,  157 

Pycnometers    158,  159 

Dr.  Squibb's  Pycnometers 160 

Graduated   Flasks 161 

Hydrometers  162,  163,  164 

Graduated  Cylinders 165 

Graduated  Glass  Measure 183 

Fletcher's  "Low  Temperature  Burner" 183 

Fletcher's  Radial  Burner 183 

Jewel  Gas  Heater ' 184 

Foot    Blower 184 

Iron    Retort , 184 

Bunsen    Burners 184,  185,  186,  188 

Erlenmeyer  Burner , 185 

Gas  Flames 186 

Roessler   Furnace 187 

Barthel's   Spirit   Lamp 188 

Wire  Cloth  for  Burners 188 

Tripods 189 

Sand-bath   Dishes 189 

Water-baths    190 

Instantaneous  Water  Heater 191 

Drying  Ovens,  Copper 192 


PART  I. 


GENERAL  PRINCIPLES  AND 
METHODS. 


CHEMICAL    PREPARATIONS. 


CHAPTER  I. 

THE    CHOICE   OF    METHODS    AND    MATERIALS. 

1.  The  methods  of  preparation  by  which  inorganic  pharma- 
ceutical  products   are   obtained  may   be  physical   processes   not 
resulting   in   any  alteration   of  the   molecules   of  the   materials 
operated  upon,  or  they  may  include  chemical  as  well  as  physical 
changes. 

Many  processes  of  preparation  are  purely  physical  changes  of 
form,  such  as  comminution,  sifting,  drying,  fusion,  sublimation, 
solution,  crystallization,  turbidation,  physical  precipitation,  gran- 
ulation, etc. 

Other  physical  processes  of  preparation  are  methods  of  separa- 
tion or  extraction,  by  which  one  or  more  of  the  component  in- 
gredients of  mixtures  are  separated.  The  means  employed  for 
this  purpose  include  fusion,  sublimation,  distillation,  solution, 
filtration,  crystallization,  physical  precipitation,  and  other 
methods. 

Processes  of  purification  are,  of  course,  also  essentially 
"methods  of  separation"  of  different  kinds  of  matter  from  each 
other;  but  distinction  may  well  be  made  between  a  mixture  of 
two  or  more  substances,  and  a  crude  product  or  natural  material 
consisting  almost  wholly  of  one  substance  contaminated  with 
small  proportions  of  other  substances  which  are  regarded  as  "im- 
purities." Processes  of  purification  are  frequently  purely  physi- 
cal processes ;  but  they  are  much  more  frequently  chemical  proc- 
esses. 

Processes  of  production  of  chemical  substances  are  always 
chemical  processes  resulting  in  the  formation  of  new  molecules. 
But  all  chemical  processes  include  physical  operations. 

2.  To  recognize  clearly  how  the  processes  employed  in  the 
laboratory  may  or  may  not  be  accompanied  by  chemical  reactions 
the  student  is  invited  to  note  the  differences  between:   I,  the 

3 


4  THE    CHOICE    OF     METHODS    AND    MATERIALS. 

purely  physical  process  of  sublimation  by  which  the  volatile  ben- 
zoic  acid  contained  in  benzoin  is  separated  from  the  non-volatile 
resin  and  other  fixed  substances  with  which  it  is  associated,  and 
the  chemical  sublimation  by  which  mercuric  chloride  is  produced 
from  a  mixture  of  mercuric  sulphate  and  sodium  chloride ;  2,  the 
purely  physical  process  of  trituration  by  which  any  single  sub- 
stance may  be  reduced  to  powder,  and  the  trituration  by  means 
of  which  mercury  and  iodine  are  brought  into  contact  with  each 
other  for  the  purpose  of  causing  them  to  unite  chemically  to  form 
mercurous  iodide;  3,  the  purely  physical  process  of  fusion  by 
which  metallic  bismuth  is  liquefied  so  that  it  may  be  run  off 
from  accompanying  infusible  minerals,  and  the  fusion  to  induce 
chemical  combination  by  which  iodine  and  arsenic  are  melted 
together  to  produce  iodide  of  arsenic ;  4,  the  simple  distillation 
by  which  the  ether  contained  in  a  mixture  of  alcohol  and  ether 
may  be  to  a  great  extent  separated  from  the  alcohol,  and  the 
chemical  distillation  by  which  ether  is  produced  and  separated 
by  distilling  it  from  a  mixture  of  alcohol  and  sulphuric  acid ;  5, 
the  simple  solution  by  which  zinc  chloride  is  dissolved  in  water, 
and  the  chemical  solution  by  which  metallic  zinc  is  dissolved  in 
hydrochloric  acid  to  form  zinc  chloride;  and  6,  the  physical  pre- 
cipitation by  which  alum  is  separated  from  its  water-solution  by 
the  addition  of  alcohol,  and  the  chemical  precipitation  by  which 
aluminum  hydroxide  is  produced  when  an  alum  solution  is  mixed 
with  a  solution  of  sodium  carbonate. 

3.  All  the  various  processes  of  preparation,  separation,  purifi- 
cation, or  production  of  chemicals  may  be  conveniently  classified 
into:  i,  dry  processes;  and  2,  wet  processes. 

Dry  processes  are  those  in  which  the  materials  employed  are 
not  liquid  at  the  ordinary  room  temperatures,  nor  dissolved  in  or 
mixed  with  any  liquid. 

The  materials  employed  in  dry  processes  are  accordingly  either 
solids  or  gases ;  but  the  solids  may  be  liquefied  by  fusion  or  the 
gases  liquefied  by  condensation.  In  most  dry  processes  the  ma- 
terials are  exclusively  solids. 

The  products  obtained  by  dry  processes  may  be  either  solids, 
liquids  or  gases ;  but  they  are  in  most  cases  solids  separable  by 
fusion  or  sublimation,  or  solids  and  gases. 

Dry  processes  include  trituration,  fusion,  sublimation,  dehy- 
dration, ignition,  calcination,  roasting,  dry  distillation. 


THE    CHOICE    OF    METHODS    AND    MATERIALS.  5 

Wet  processes  are  those  in  which  the  materials  employed  include 
liquids,  whether  the  liquid  or  liquids  employed  constitute  chemi- 
cal factors  or  are  used  as  simple  solvents  or  other  physical  media 
to  promote  the  attainment  of  the  ends  sought. 

The  products  of  wet  processes  may  be  solids,  liquids,  or  gases. 

The  wet  processes  include  solution,  crystallization,  precipita- 
tion, distillation,  and  various  other  methods. 

4.  The  choice  of  method  must  be  determined  by :    I,  the  nature 
of  the  product  sought ;  2,  the  materials  available  for  its  produc- 
tion ;  3,  the  nature  of  the  bye-products,  if  any ;  and  4,  the  chemi- 
cal laws  governing  the  behavior  of  factors  and  products  in  all 
cases  where  the  results  depend  upon  chemical  changes  or  reac- 
tions. 

Among  the  most  important  facts  to  be  considered  are  the  state 
of  cohesion,  relative  water-solubility  and  relative  volatility  of  the 
products  and  materials ;  then  the  various  chemical  reactions  which 
may  be  utilized  to  convert  the  different  available  materials  into 
the  products  desired,  and  the  separability  of  the  several  products 
from  each  other  when  more  than  one  product  is  formed. 

5.  Most  of  the  chemical  products  are  solids.     For  the  pur- 
poses of  this  treatise  we  shall  classify  the  solid  chemical  products 
into  soluble  solids  and  insoluble  solids;  into  volatile  solids  and 
non-volatile  solids;  and  into  fusible  solids  and  infusible  solids. 

The  water-soluble  metallic  salts  are  very  generally  produced 
from  the  corresponding  acids.  Thus  the  water-soluble  metallic 
nitrates  are  generally  made  from  nitric  acid,  sulphates  from  sul- 
phuric acid,  chlorides  from  hydrochloric  acid,  acetates  from  acetic 
acid,  and  so  on.  The  processes  employed  for  this  purpose  are 
chemical  solution,  saturation  or  neutralization,  followed  by  the 
requisite  method  of  separation  of  the  products  from  the  bye- 
products.  The  materials  required  in  addition  to  the  acids  are  the 
metals  themselves  or  their  oxides,  hydroxides  or  carbonates  or 
other  compounds  yielding  unobjectionable  bye-products — water 
or  gases. 

The  water-soluble  metallic  compounds  may  also  be  made  by 
double  decomposition  between  factors  producing  insoluble  bye- 
products. 

Insoluble  metallic  compounds  are  most  frequently  made  by  pre- 
cipitation, the  materials  employed  being  water-solutions  of  the 
required  factors  and  the  bye-products  being  water-soluble. 


6  THE    CHOICE    OF    METHODS    AND    MATERIALS. 

Volatile  solids  may  be  made  by  sublimation  if  no  volatile  bye- 
product  be  formed. 

Non-volatile  solids,  when  not  produced  by  chemical  solution  or 
by  precipitation,  may  be  made  by  various  dry  processes,  including 
double  decomposition  between  dry  materials  if  the  bye-product 
be  volatile  so  that  it  may  be  eliminated  by  sublimation  or  by  dissi- 
pation with  the  aid  of  heat. 

Fusible  solids  are  frequently  made  by  fusion  when  the  bye- 
product,  if  any,  is  infusible  so  that  separation  is  practicable. 

Liquid  products  are  generally  produced  by  chemical  distil- 
lation, or  by  chemical  solution. 

6.  Gases  are  generally  produced  by  metathesis,  or  by  dissocia- 
tion, at  high  temperatures. 

7.  From  the  facts  mentioned  in  the  preceding  paragraphs  the 
student  will  note  that  the  separability  of  the  products  is  an  ex- 
tremely important  factor  in  the  selection  of  methods  for  the  pro- 
duction of  chemicals.     Assuming  that  two  products  are  formed 
(which  is  generally  the  case),  they  may,  of  course,  be  readily 
separated  and  the  process  thus  rendered  practicable:     I,  if  one 
product  be  soluble  and  the  other  insoluble ;  2,  if  one  product  be 
non-volatile  and  the  other  volatile ;  3,  if  one  is  a  fusible  solid  and 
the  other  infusible;  4,  if  one  be  a  gas  and  the  other  a  solid  or 
liquid  at  the  temperature  of  the  reaction;  and  5,  if  one  product 
be  water  or  some  other  liquid  which  is  unobjectionable  or  easily 
separated  from  the  other  product. 

8.  But  two  or  more  soluble  salts  contained  together  in  one 
solution  or  mixture  may  frequently  be  separated  from  each  other 
(6)  if  they  differ  materially  in  their  respective  ratios  of  solubility 
in  the  same  solvent  at  any  conveniently  attainable  temperature ; 
or  (7)  if  one  be  soluble  without  alteration,  and  the  other  insoluble, 
in  another  liquid  miscible  without  chemical  reaction  with  the  com- 
mon solvent  for  both. 

Thus  if  A  and  B  be  both  contained  in  nearly  equal  proportions 
in  solution  in  the  same  water  and  if  A  be  freely  soluble  while  B 
is  only  sparingly  soluble,  it  follows  that  when  the  solution  is  con- 
centrated by  evaporation  B  must  separate  from  the  solution  before 
A.  And  if  A  and  B  be  both  contained  in  solution  in  the  same 
water  and  if  A  be  insoluble  in  alcohol  and  in  diluted  alcohol  while 
B  is  soluble  in  either,  then  A  must  be  precipitated  on  the  addition 
of  alcohol  while  B  remains  in  the  liquid. 


THE    CHOICE    OF     METHODS    AND    MATERIALS.  7 

9.  The  prognosis  of  the  reactions  which  will  probably  take 
place  between  the  factors  brought  into  contact  with  each  other  in 
any  chemical  process  is  generally  rendered  practicable  by  a  good 
knowledge  of  the  conditions  which  are  known  to  affect  their  direc- 
tion and  relative  completeness,  such  as:     I,  the  quality,  quantity 
and  intensity  of  the  chemical  combining  power  of  the  elements 
composing  the   factors   of  the   reaction,   including  the   greater 
energy  of  radicals  in  the  nascent  state ;  2,  the  influence  of  predis- 
posing affinity ;  3,  the  freedom  of  contact  between  the  factors,  in- 
cluding the  removal  of  one  of  the  products  from  the  scene  of 
action  and  the  influence  in  that  direction  of  the  cohesion,  solu- 
bility, fusibility  and  volatility  of  the  products ;  4,  the  influence  of 
temperature;  and  5,  the  relative  masses  of  the  reacting  sub- 
stances. 

These  matters  were  discussed  in  Chapter  XIX  of  Vol.  I. 

10.  The  different  forms  of  chemical  reaction  were  fully  de- 
scribed in  Chapter  XVII  of  Vol.  I.    The  most  common  reactions 
by  which  inorganic  chemical  products  are  formed  are:  Dissocia- 
tion, or  decomposition ;  Synthesis,  or  combination  or  composition  ; 
Metathesis,  or  double  decomposition,  including  Substitution;  and 
reactions  of  Oxidation  and   Reduction,    or    reactions    involving 
changes  of  atomic  polarity-value. 

11.  The  choice  of  materials.    The  factors  or  materials  that  can 
be  used  for  the  production  of  chemical  preparations  may  generally 
be  any  substances  containing  or  furnishing  the  elements  composing 
the  product  sought.  Thus  any  compound  of  mercury  can  be  made 
out  of  any  other  compound  of  mercury,  and  any  iodide  can  be 
employed  for  the  preparation  of  any  other  iodine  compound. 

But  the  best  materials  are  those  that  give  satisfactory  results 
with  the  least  expenditure  of  time  and  labor  and  at  the  least  cost. 
Hence  we  would  not  make  mercuric  iodide  out  of  mercuric  sul- 
phate, nor  out  of  aristol  or  any  other  expensive  or  complex  iodine 
compound. 

The  materials  necessary  are  generally  in  any  given  case,  two: 
one  of  them  to  contribute  the  positive  radical  and  the  other  to 
contribute  the  negative  radical  of  the  product  sought. 

There  are  usually  several  kinds  of  inexpensive  materials  avail- 
able; but  the  cheapest  materials  frequently  demand  the  most 
tedious  and  expensive  processes,  while  easy  and  inexpensive 
methods  are  generally  applicable  when  the  materials  are  of  a 


8  THE    CHOICE    OF    METHODS    AND    MATERIALS. 

higher  grade.  Cheap  raw  materials  are,  therefore,  used  only  in 
manufacturing  on  a  large  scale  with  all  the  labor-saving  devices 
and  special  facilities  requisite  to  obtain  satisfactory  results  at  the 
least  cost. 

To  prepare  pharmaceutical  chemicals  and  other  pure  chemical 
products  it  is  necessary  to  employ,  as  far  as  practicable,  materials 
of  definite  composition  and  free  from  any  impurities  that  can  not 
be  easily  removed  in  the  process  adopted.  Unfit  materials  furnish 
unfit  products. 

12.  The  most  common  materials  employed  for  the  production 
of  pure  inorganic  chemicals  are: 

Acids  and  their  solutions. 

Alkalies  and  their  solutions. 

The  metals. 

Metallic  oxides. 

Metallic  hydroxides. 

Metallic  carbonates. 

Soluble  metallic  sulphates,  nitrates,  phosphates,  acetates  and 
other  soluble  metallic  oxygen  salts. 

Soluble  metallic  chlorides,  bromides  and  iodides. 

The  non-metallic  elements  chlorine,  bromine,  iodine,  sulphur 
and  carbon. 

13.  Whenever  solutions  of  acids,  alkalies,  or  salts,  or  other 
solutions  are  employed  as  materials,   it  is  necessary  that  their 
strength  shall  be  exactly  determined  and  that  the  relative  pro- 
portions used  be  governed  accordingly,  and  the  quantities  pre- 
scribed in  stated  formulas  must  be  corrected  in  every  instance  as 
required. 

The  actual  strength  of  acids,  ammonia  water,  and  other  solu- 
tions frequently  varies  materially  from  the  official  or  commonly 
recognized  standards  and  from  the  strength  specified  on  the  label 
or  indicated  by  the  title. 

If  the  materials  be  crystallized  substances  containing  water  of 
crystallization  they  must  be  in  perfect  condition,  either  containing 
the  known  full  amount  of  such  water,  or  dried  until  they  cease 
to  lose  weight  or  attain  a  definite  composition  in  accordance  with 
which  the  proportion  required  for  the  reaction  may  be  exactly 
determined.  It  is  clear  if  100  Gm.  of  crystallized  sodium  car- 
bonate is  required,  that  100  Gm.  of  effloresced  sodium  carbonate 
must  be  too  much ;  and  that  if  one  kilogram  of  an  anhydrous  salt 


THE    CHOICE    OF     METHODS    AND    MATERIALS.  Q 

is  required  the  same  quantity  of  a  salt  containing  one  molecule  of 
water  of  crystallization  is  insufficient,  and  a  kilo  of  a  salt  contain- 
ing several  molecules  of  crystal  water  must  be  still  farther  from 
the  correct  amount. 

Whenever  hygroscopic  substances  are  used  they  must  be  per- 
fectly dry;  or,  if  the  moisture  be  unobjectionable,  its  exact  pro- 
portion must  be  known  and  taken  into  account,  for  it  one  pound 
of  dry  potassium  carbonate  or  potassium  cyanide  is  required,  one 
pound  of  wet  carbonate  or  cyanide  will  not  be  enough. 

14.  Acids  employed  in  the  laboratory  must  be  tested  both 
qualitatively  and  quantitatively  before  they  can  be  safely  used. 
Their  strength  can  not  be  sufficiently  accurately  determined  by 
their  respective  specific  weights ;  it  must  be  ascertained  by  vol- 
umetric analysis.     Should  it  be  found  to  differ  from  that  upon 
which  the  proportions  in  the  working  formula  are  based,  those 
proportions  must  be  corrected  to  correspond  with  the  acid  used  or 
the  strength   of  the  acid  must  be  changed  to  accord  with  the 
formula. 

If  the  Pharmacopoeia  prescribes  a  sulphuric  acid  of  "not  less 
than  92.5  per  cent"  strength,  and  bases  all  its  working  formulas 
in  which  that  acid  is  prescribed  upon  the  assumption  that  the  acid 
employed  contains  neither  more  nor  less  than  92.5  per  cent  of 
absolute  H2SO4,  then  the  sulphuric  acid  usually  sold  may  fre- 
quently be  found  of  such  strength  as  to  require  the  correction  of 
the  proportional  amount  ordered. 

Other  chemical  solutions  must  be  tested  in  the  same  manner — 
by  volumetric  assay — and  the  quantity  used  made  to  conform  to 
the  actual  strength  found. 

15.  The  water-soluble  salts  of  any  metal  are  most  frequently 
made  out  of  insoluble  compounds  of  that  metal  if  not  from  the 
metal  itself,  and  insoluble  metallic  compounds  are  generally  pro- 
duced from  soluble  compounds. 


CHAPTER    II. 

CRUSHING   AND    POWDERING. 

16.  It  is  frequently  necessary  to  crush  solid  substances  pre- 
paratory to  their  use  as  materials. 

A  large  piece  may  be  broken  on  the  anvil  with  a  hammer,  or 
in  an  iron  mortar  by  well  directed  blows  with  the  pestle.  To 
prevent  the  fragments  from  being  scattered  the  piece  may  first 
be  wrapped  in  several  thicknesses  of  strong  paper. 

Crushing  machines  or  iron  mills  are  useful  for  coarse  comminu- 
tion when  the  substance  to  be  crushed  or  coarsely  ground  does 
not  consist  of  or  contain  pieces  too  large  to  be  put  through  the 
machine. 

Hard  and  tough  minerals  like  manganese  dioxide  in  lumps, 
haematite,  iron  sulphide,  antimony  sulphide,  marble,  and  other 
materials  used  in  considerable  quantities,  may  be  advantageously 
broken,  crushed,  and  even  powdered,  in  a  deep  iron  mortar. 

17.  Some  minerals  which  are  too  unyielding  to  be  crushed  and 
powdered  in  the  iron  mortar  without  other  aids  may  be  heated 
to  dull  redness,  or  near  it,  and  then,  while  hot,  dropped  into  cold 
water.    This  treatment  sometimes  renders  such  substances  much 
more  tractable.    Haematite  can  be  reduced  in  that  manner.    This 
plan  is,  of  course,  not  applicable  to  substances  which  are  decom- 
posed or  fused  by  the  high  temperature. 

18.  The  iron  mortar  must  be  large  and  deep,  and  the  pestle 
heavy  enough  to  do  a  considerable  portion  of  the  work  of  con- 
tusion by  its  own  weight. 

Small  mortars  are  practically  useless  for  such  purposes  as  the 
crushing  and  pulverization  of  hard  and  tough  substances,  because 
the  quantity  operated  upon  at  one  time  must  not  be  greater  than 
that  barely  sufficient  to  cover  the  bottom  of  the  mortar  to  the 
depth  of  about  10  to  50  millimeters,  according  to  its  size. 

An  iron  mortar  about  0.50  meter  deep  and  0.25  meter  in 
diameter  is  perhaps  most  useful  in  the  average  laboratory,  being 
sufficient  for  the  effective  contusion  of  as  large  quantities  as  can 
be  conveniently  treated  all  at  once,  and  not  too  large  for  much 

10 


CRUSHING  AND  POWDERING. 


II 


smaller  quantities.  When  a  very  large  quantity  of  any  material 
is  to  be  crushed  or  powdered  it  is,  of  course,  necessary  to  divide 
it  into  portions  not  too  large  for  effective  work. 

A  larger  iron  mortar  is  probably  too  heavy  for  general  labora- 
tory use,  but  an  additional  mortar  of  about  one-third  the  dimen- 
sions specified  will  be  found  useful  occasionally. 

Being  very  heavy  the  large  iron  mortar  should  be  placed  firmly 
upon  a  solid  foundation,  preferably  on  a  wooden  block  fixed  in  the 
ground  and  resting  on  a  large  stone. 


Fig.  1.  Large  iron  mortar. 


M 


Fig.  3.  Shallow  iron  mortar. 


The  iron  mortar  and  pestle  are  more  generally  useful  and  ef- 
fective than  any  crushing  machines  or  mills  for  ordinary  opera- 
tions. Insoluble  solids  rarely  attack  iron  and  may  be  powdered 
in  the  iron  mortar  without  becoming  contaminated  with  iron. 
Even  soluble  chemicals  may  frequently  be  safely  permitted  to 
come  in  contact  with  iron ;  but  the  mortar  and  pestle  must  be  at 
all  times  kept  bright  and  clean — quite  free  from  rust. 

Perfectly  dry  chemicals  can  usually  be  safely  pulverized  in  a 
bright,  dry  iron  mortar ;  but  moist  chemicals  and  such  as  contain 


12  CRUSHING  AND  POWDERING. 

water  of  crystallization  should  be  powdered  in  porcelain  mortars. 

Very  brittle  or  friable  substances  that  can  be  easily  crushed  and 

reduced  to  powder  by  trituration  in  a  porcelain  mortar  should  not 

be  powdered  in  the  iron  mortar;  nor  should  any  acid  Or  alkali, 


Fig.  4.  Steel  spatula  used  with  small 
iron  mortars  and  iron   dishes. 

or  other  substance  which  may  act  chemically  upon  the  iron,  be 
placed  in  it. 

19.  Porcelain  mortars  for  crushing  and  powdering  chemicals, 
and  for  mixing  powdered  materials,  should,  like  the  iron  mortar, 
be  very  capacious  in  proportion  to  the  quantities  triturated  at 


Fig.  5.  Trituration  mortar  of  porcelain. 

one  time  in  them,  but  not  so  deep.  Several  sizes  of  porcelain 
mortars  are  required,  varying  from  100  to  400  millimeters  in 
diameter  and  of  a  depth  equal  to  about  two-thirds  of  the  diameter. 
It  is  very  important  that  every  mortar  shall  have  a  regular, 
spherically  concave,  smooth  bottom,  free  from  "nipples"  and 
"wrinkles,"  or  from  elevations  or  irregular  depressions  of  any 
kind,  and  that  its  pestle  shall  fit  it  perfectly.  .The  convex  head 
of  the  pestle  must  be  large  and  perfectly  spherical,  but  of  a 
slightly  smaller  radius  than  that  of  the  curved  bottom  or  grinding 
surface  of  the  mortar.  The  handle  of  the  pestle  must  be  large 
and  strong  so  that  it  can  be  firmly  grasped  with  the  whole  hand 


CRUSHING  AND  POWDERING.  13 

in  order  that  sufficient  pressure  may  be  conveniently  exercised  in 
the  act  of  triturating. 

Effective  trituration  is  impracticable  when  the  quantity  of 
material  contained  in  the  mortar  is  too  great,  and  the  best  results 
are  attained  when  the  layer  of  powder  is  not  greater  than  that  re- 
quired to  well  cover  the  bottom  of  the  mortar. 

When  large  crystals  are  to  be  broken  or 
crushed  in  the  porcelain  mortar,  sufficient  care 
should  be  exercised  to  prevent  the  scattering 
of  the  fragments,  and  it  is  sometimes  best  to 
wrap  the  large  crystal  or  piece  in  muslin  or  Fig.  e.  small  porcelain 

mortar. 

paper. 

Only  comparatively  brittle  substances  can  be  easily  powdered 
by  trituration. 

20.  When  dry  poisonous  substances  are  triturated  in  a  mortar, 
care  must  be  taken  to  prevent  the  danger  from  dust  rising  out  of 
the  mortar.     It  is  sometimes  advisable  to  moisten  the  contents 
of  the  mortar  with  water  or  alcohol  if  admissible.    Arsenous  oxide 
and  mercuric  oxide  are  good  examples  of  substances  that  ought 
not  to  be  triturated  or  sifted  in  a  dry  condition  if  considerable 
quantities  are  thus  treated  so  that  the  operations  are  too  extensive 
and  extended  to  be  safe. 

21.  The  spatula  is  indispensable  in  employing  trituration  as  a 
means  of  reducing  substances  to  fine  powder  and  in  mixing  pow- 
dered materials,  for  most  substances  have  a  tendency  to  adhere 


Fig.  7.  Steel  spatula. 

more  or  less  to  the  surfaces  of  mortars  and  pestles  when  triturated 
under  pressure,  and  must  be  scraped  off  with  the  spatula. 

22.  Levigation  is  the  trituration  of  a  powder  to  an  extremely 
fine  state  of  division  on  a  slab  with  a  muller,  adding  a  liquid,  as 
either  water  or  oil,  to  form  a  very  soft  paste  with  the  powder. 
But  the  levigation  may  also  be  very  advantageously  effected  in  a 
perfect  mortar  with  a  perfect  pestle,  instead  of  using  a  slab  and 
muller. 

23.  Sometimes    levigation    is    followed   by   elutriation.     This 
process  consists  in  agitating  finely  powdered  insoluble  substances 
with  large  quantities  of  water,  then  permitting  the  coarser  par- 


CRUSHING  AND   POWDERING. 


tides  to  subside  during  a  brief  cessation  of  the  agitation,  after 
which  the  liquid,  holding  the  finest  powder  still  in  suspension,  is 
decanted  into  another  vessel.  By  repeated  alternate  levigation 
and  elutriation  the  product  may  thus  be  reduced  to  an  "impal- 
pable" or  extremely  fine  powder.  Prepared  chalk  and  purified 
antimony  sulphide  are  thus  treated. 

24.  Dry  substances  which  have  been  powdered  by  grinding, 
contusion  or  trituration  require  sifting  if  it  is  necessary  to  render 
their  fineness  uniform  or  to  remove  any  coarse  particles  the  pow- 
ders may  contain.    The  sieves  may  be  made  of  hair  cloth,  silk,  or 
brass  wire  gauze.    The  finest  powders  are  sifted  through  bolting 
cloth  of  silk.    Insoluble  inorganic  substances  should  be  reduced  to 
the  finest  powder  attainable,  and  should  in  no  case  be  coarser  than 
No.  80. 

The  numbers  employed  to  designate  the  fineness  of  powders 

are  also  applied  to  the  sieves,  and  they 
refer  to  the  meshes  or  openings  to  each 
linear  inch.  Thus  a  No.  80  sieve  is 
one  having  80  meshes  to  each  linear 
inch  of  the  sieve  cloth,  and  a  No.  80 
powder  is  one  that  has  been  passed 
through  such  a  sieve.  It  were  better 
if  the  diameter  of  each  mesh  were 
given  for  the  meshes  are  not  always 
square  and  the  wire,  hair,  or  thread, 
not  always  of  the  same  calibre. 
As  finely  powdered  inorganic  substances  are  generally  light 
enough  to  rise  into  the  air  when  sifted  in  an  open. sieve,  making 
the  operation  very  troublesome  on  account  of  the  dust,  it  is  cus- 
tomary to  use  drum  sieves,  or  sieves  provided  with  covers  above 
and  receptacles  below.  These  covers  are  made  of  drum  skin  in 
wooden  frames  like  those  in  which  the  sieve  cloth  is  placed,  or 
the  sieve  frame  and  covers  are  made  of  brass  or  of  tinned  iron. 
For  sifting  insoluble  inorganic  substances  the  drum  sieves  made 
wholly  of  metal  are  generally  most  useful. 

25.  Very  friable  soft  masses  of  dried  precipitates,  such  as 
those  of  magnesium  carbonate,  bismuth  subnitrate,  bismuth  sub- 
carbonate,  etc.,  can  be  powdered  by  gently  rubbing  them  through 


Fig.  8.  Metal  sieve  with  covers, 
or  drum  sieve. 


CRUSHING  AND   POWDERING.  15 

the  sieve  cloth  with  a  comparatively  soft  brush,  or  by  rubbing 
the  pieces  against  the  brass  wire  cloth  in  the  sieve. 

Powders  should  never  be  forced  through  the  sieve  if  a  soft  and 
fine  product  is  desired,  and  a  fine  soft  powder  should  be  made  in 
every  case  where  it  is  possible. 

26.  Zinc,  tin,  and  some  other  readily  fusible  metals  may  be 
reduced  to  small  pieces,  or  "granulated,"  by  pouring  the  melted 
metal  into  a  pan  or  bucket  of  water. 

27.  Coarse  powder  or  granular  products  may  be  obtained  by 
precipitation,  granulation,  and  turbidation,  described  elsewhere. 


CHAPTER  III. 

DRY    CHEMICAL     PROCESSES. 

28.  Reactions  induced  by  trituration.    A  few  chemical  com- 
pounds and  pharmaceutical  chemicals  of  indefinite  composition 
can  be  produced  by  triturating  the  dry  materials  together.    Long 
continued  trituration  and  strong  pressure  are  necessary  in  such 
cases.    Chemical  reactions  brought  about  in  this  way  are  generally 
incomplete,  and  the  products  accordingly  impure  and  unsatisfac- 
tory. 

Anhydrous  substances  and  many  other  perfectly  dry  chemicals 
may  sometimes  be  intimately  mixed  with  each  other  by  light 
trituration  without  any  chemical  reaction;  this  happens,  too,  in 
cases  where  at  least  partial  reaction  takes  place  between  the  same 
materials  if  triturated  together  under  strong  pressure  or  if  water 
is  added. 

Crystallized  hydrous  salts  when  triturated  together  may  react 
upon  each  other  and  a  wet  mixture  may  be  obtained  without  the 
addition  of  any  moisture  on  account  of  the  liberation  of  the  water 
of  crystallization. 

When  dry  solids  unite  chemically  under  strong  trituration  the 
synthesis  may  develop  so  high  a  temperature  that  means  must  be 
taken  to  control  it.  Thus  alcohol  is  added  when  mercury  and 
iodine  are  rubbed  together  to  form  iodide  of  mercury ;  the  evap- 
oration of  the  alcohol  then  lowers  the  temperature  and  prevents 
the  loss  of  iodine  by  vaporization. 

29.  Fusion  is   frequently  resorted  to  in  chemical  operations, 
sometimes  simply  to  separate  fusible  from  infusible  substances, 
but  in  other  cases  to  induce  chemical  reactions  between  the  mate- 
rials fused  together. 

Whenever  the  object  is  to  induce  chemical  reaction  the  mate- 
rials should,  if  practicable,  first  be  powdered  and  well  mixed. 
The  temperature  required  to  produce  fusion  is  obtained  partly 
from  the  heat  applied  to  start  the  reaction  and  partly  from  the 
heat  generated  by  the  reaction  itself  when  once  started. 

The  vessels  in  which  substances  are  fused  differ  widely,  accord- 

16 


DRY    CHEMICAL    PROCESSES.  I/ 

ing  to  the  temperature  necessary.  The  fusion  may  in  some  cases 
be  accomplished  in  glass  beakers  or  bottles,  or  in  porcelain  dishes 
or  crucibles,  at  temperatures  below  the  boiling  point  of  water ;  in 
other  cases  "red  heat,"  or  even  "white  heat,"  is  required,  and 
crucibles  must  then  be  used  which  are  made  of  materials  such  as 
can  be  subjected  to  that  high  heat  without  risk.  The  principal 
materials  out  of  which  such  crucibles  are  made  include  fire-clay, 
graphite,  and  platinum. 

Clay  crucibles  are  more  or  less  porous  and  are  also  liable  to 
crack;  accordingly  they  can  not  be  used  more  than  once  except 
for  the  same  substances,  and  then  only  two  or  three  times.  Gra- 
phite crucibles  do  not  crack  so  easily,  nor  are  they  porous ;  but 
they  are  soon  burnt  out.  A  combination  of  clay  and  graphite  is 


and  10.  Clay  crucibles.  Fig.  11.  Graphite   crucibles. 


sometimes  used  and  to  good  advantage.  Platinum  crucibles  are 
necessary  for  many  operations;  but  do  not  resist  the  chemical 
action  of  certain  substances. 

When  fusion  is  effected  it  is  to  be  remembered  that  so  long 
as  any  of  the  fusible  solid  substance  remains  to  be  liquefied  the 
temperature  of  the  contents  of  the  vessel  in  which  the  fusion  is 
performed  remains  practically  stationary ;  but  that,  as  soon  as  all 
of  the  fusible  matter  has  been  reduced  to  the  liquid  state,  the 
temperature  may  rise  very  rapidly  if  the  application  of  strong 
heat  from  without  be  continued,  and  that  in  cases  where  a  too 
high  temperature  is  liable  to  do  damage,  it  may  be  necessary  to 
promptly  remove  the  crucible  or  other  vessel  from  the  fire  or  to 
discontinue  the  heating  before  any  damage  is  done. 

Fusion  is  exemplified  in  processes  of  purification  of  bismuth, 
antimony  sulphide,  and  many  other  substances,  and  in  the  prepar- 
ation of  moulded  and  diluted  silver  nitrate,  fused  calcium  chloride, 

Vol.   II— 2 


l8  DRY    CHEMICAL    PROCESSES. 

granulated  zinc,  the  iodides  of  arsenic  and  sulphur,  potassium 
cyanide  and  sulphurated  potassa. 

Distinction  is  to  be  made  between  true  fusion  (sometimes  called 
"igneous  fusion,"  when  accomplished  at  a  very  high  tempera- 


Fig.  12  and  13.  Crucible  tongs. 

ture),  and  the  solution  of  hydrous  crystallized  salts  in  their  own 
water  of  crystallization  when  heated  (which  is  called  "aqueous 
fusion)."  See  par.  33. 

30.  Ignition  without  fusion  always  has  for  its  object  a  greater 
or  less  change  in  the  composition  of  the  substance  heated.    These 
changes  include  the  expulsion  of  volatile  impurities,  the  expulsion 
of  water,  dissociation,  oxidation,  and  various  intramolecular  rear- 
rangements of  the  atomic  linking. 

Ignition  is  effected  in  iron  pots,  clay  crucibles,  and  other  ves- 
sels, and  generally  at  very  high  temperatures.  The  substances  to 
be  subjected  to  ignition  are,  if  practicable,  first  powdered,  and 
when  two  or  more  substances  are  to  be  ignited  together  they  are 
first  mixed  with  each  other  as  intimately  as  possible. 

Exsiccation,  calcination,  and  dry  oxidation  are  examples  of 
ignition. 

31.  Dehydration  of  solids.     The  removal  of  water  held  by 
chemical  products  is  called  dehydration.    It  is  effected  by  various 
methods  of  drying. 

Hygroscopic  moisture  may  be  expelled  from  solids  by  desicca- 
tion. The  heat  applied  for  this  purpose  must  be  sufficient  to  ac- 
complish the  object  without  unnecessary  loss  of  time,  but  not  so 
high  that  the  product  may  be  injured  or  lost  by  decomposition  or 
volatilization.  The  solid  substance  in  coarse  or  fine  powder  or  in 
a  granular  or  crystalline  condition,  according  to  its  nature,  is 
spread  out  over  the  bottom  of  a  shallow  dish  and  carefully  heated. 
It  must  be  constantly  or  frequently  stirred  during  the  process  of 
desiccation,  and  when  quite  dry  the  product  should  be  at  once  put 


DRY    CHEMICAL    PROCESSES.  IQ 

into  prefectly  dry,  warm  containers,  which  must  be  tightly  closed. 

Some  solids  must  be  kept  in  fusion  for  some  time  in  order  to 
render  them  anhydrous. 

Unstable  or  volatile  solids  when  moist  may  often  be  successfully 
dried  over  lime,  sulphuric  acid,  or  other  substances  having  a  great 
avidity  for  water.  This  method  of  desiccation  will  be  described 
later. 

Water  of  crystallization  is  eliminated  by  efflorescence  or  by  ex- 
siccation. 

32.  The  partial  or  complete  removal  of  water  of  crystalliza- 
tion at  common  room  temperatures,  or  its  gradual  expulsion  by 
moderate  heat,  is  called  efflorescence. 

Substances  which  crystallize  with  several  molecules  of  water 
do  not  hold  all  of  that  water  with  equal  force.  Thus  many  salts 
lose  a  portion  of  the  water  of  crystallization  at  about  20°  or  35° 
to  40°  or  60°,  but  retain  the  remainder  at  higher  temperatures. 
(See  also  par.  34.) 

Several  substances  which  give  up  a  portion  of  their  water  of 
crystallization  at  the  common  room  temperatures  in  dry  air  do 
not  effloresce  at  the  same  temperatures  in  moist  air. 

When  the  gradual  efflorescence  of  a  salt  is  desired  the  tempera- 
ture must  be  regulated  according  to  the  known  results  of  expe- 
rience with  that  particular  salt,  for  no  general  rule  is  applicable  to 
different  salts. 

Large  crystals  should  be  broken  into  small  fragments  before 
being  exposed  to  the  air  to  effloresce. 

The  efflorescence  should  be  effected  in  a  current  of  dry,  warm 
•air,  and  the  substance  subjected  to  this  treatment  should  be  spread 
out  in  a  thin  layer  and  occasionally  stirred. 

Drying  closets  are  necessary  in  all  laboratories  where  chemical 
products  are  made  in  considerable  quantities. 

33.  Some  readily  water-soluble  substances  in  the  form  of  crys- 
tals containing  much  water  of  crystallization   dissolve  in  their 
crystal-water  when  heated    They  are  then  said  to  undergo  aqueous 
fusion.    Alum,  sodium  phosphate,  sodium  carbonate,  ferrous  sul- 
phate, sodium  sulphate,  and  several  other  salts  may  be  easily  dis- 
solved in  their  own  water  of  crystallization  by  heating  the  crystals. 
When  the  temperature   is   raised  above  that  required  to  cause 
aqueous  fusion,  the  salt  begins  to  give  up  its  crystal-water,  and 


20  DRY    CHEMICAL    PROCESSES. 

finally  becomes  dry  although  it  may  still  retain  some  molecularly 
combined  water  if  the  temperature  is  insufficient  to  expel  all. 

34.  The  amount  of  water  of  crystallization  expelled  by  heat 
depends  upon  the  temperature.     If  the  substance  contains  two  or 
more  molecules  of  water  it  may  give  up  one  or  more  molecules  at 
one  given  temperature,  and  other  molecules  of  it  at  certain  definite 
higher  temperatures. 

Sodium  arsenate  loses  all  of  its  seven  molecules  of  water  at 
about  149°  ;  but  five  molecules  of  it  are  expelled  by  complete  ef- 
florescence at  a  gentle  heat. 

35.  Exsiccation  is  a  term  used  to  signify  the  expulsion  of 
water  of  crystallization  by  the  aid  of  heat. 

Dried  sodium  carbonate,  sodium  sulphate,  sodium  phosphate, 
alum,  ferrous  sulphate,  magnesium  sulphate,  and  several  other  ex- 
siccated salts  are  common  preparations. 

Such  preparations  are  not  always  anhydrous,  but  each  exsic- 
cated salt  if  not  anhydrous  must  contain  a  definite  amount  of 
water. 

The  "dried  alum"  of  the  Pharmacopoeia  must  be  anhydrous ; 
"dried  ferrous  sulphate"  must  consist  of  two  molecules  of 
FeH2SO5  with  not  over  one  molecule  of  water;  "dried  sodium 
carbonate"  of  the  Pharmacopoeia  contains  two  molecules  of  water ; 
and  anhydrous  sodium  carbonate  is  also  used. 

In  order  to  obtain  products  of  definite  composition  by  exsicca- 
tion it  is  necessary  that  the  crystallized  or  effloresced  solids  shall 
be  subjected  to  a  fixed  degree  of  heat  until  they  cease  to  lose 
weight. 

It  is  generally  (but  not  always)  advantageous  to  reduce  crys- 
tallized salts  to  coarse  powder  before  they  are  subjected  to  exsic- 
cation. In  some  cases  a  softer  product  is  obtained  when  the 
crystallized  salt  is  first  effloresced  at  a  temperature  sufficiently  low 
to  prevent  aqueous  fusion,  and  the  exsiccation  completed  at  the 
lowest  temperature  sufficient  to  expel  all  of  the  water  which  it  is 
desired  to  eliminate. 

In  all  operations  of  efflorescence  and  exsiccation  it  is  important 
that  the  product  be  well  protected  against  contamination  by  dust. 

36.  Dry  dissociation  of  chemical  compounds  yielding  gaseous 
decomposition-products  occurs   in  various  laboratory  processes. 
The  production  of  oxygen  by  heating  either  potassium  chlorate 
or  mercuric  oxide,  and  other  dry  gas-operations,  and  the  conver- 


DRY    CHEMICAL    PROCESSES.  21 

sion  of  phosphates  into  pyrophosphates,  illustrate  the  decomposi- 
tion of  chemical  compounds  in  a  solid  state  by  heat. 

But  the  most  common  example  of  dry  dissociation  by  heat  is 
the  production  of  metallic  oxides  by  strongly  heating  the  hy- 
droxides, nitrates,  oxalates,  sulphates  or  other  salts  affording 
volatile  bye-products.  This  is  called  calcination,  and  it  is  so 
named  because  lime  (calx)  or  calcium  oxide  is  obtained  by 
strongly  heating  calcium  carbonate  in  lime  kilns. 

Among  the  metallic  oxides  that  may  be  prepared  by  calcination 
are :  magnesium  oxide,  from  the  hydroxide  or  the  carbonate ;  the 
oxides  of  calcium,  strontium  and  barium,  from  the  hydroxides 
or  the  carbonates ;  ferric  oxide,  from  the  hydroxide  or  the  oxalate ; 
cupric  oxide,  from  the  hydroxide  or  the  nitrate ;  zinc  oxide,  from 
the  hydroxide  or  the  carbonate ;  mercuric  oxide,  from  the  nitrate ; 
lead  oxide,  from  the  hydroxide  or  the  carbonate  or  nitrate;  and 
bismuth  oxide,  from  the  hydroxide. 

37.  Dry  oxidation  is  often  effected  by  the  combustion  of  metals 
in  free  access  of  air,  or  by  the  ignition  of  reducing  agents  with 
oxidizing  agents,  or  by  roasting  metallic  sulphides. 

Among  the  metallic  oxides  that  can  be  produced  by  the  oxida- 
tion of  the  metals  in  air  we  have  magnesium  oxide,  zinc  oxide, 
lead  oxide  and  mercuric  oxide. 

The  oxides  of  zinc,  lead,  antimony  and  some  other  metals  can 
be  made  by  "roasting"  their  sulphides  in  the  air. 

Arsenites  may  be  oxidized  to  arsenates  by  ignition  with  nitrates, 
and  other  analogous  dry  oxidations  may  be  effected  with  various 
oxidizing  agents  such  as  manganese  dioxide,  potassium  dichro- 
mate,  and  lead  dioxide. 

38.  Sublimation.     Volatile  solids  may  be  vaporized  and  the 
vapor  condensed  to  the  solid  state  again  either  in  the  upper  and 
cooler  portions  of  the  same  vessels  in  which  the  solid  substances 
are  heated,  or  in  suitable  receivers  connected  therewith. 

The  vessels  employed  are  special  flasks  or  retorts  of  glass,  earth- 
enware or  metal,  and  the  condensing  receptacles,  if  any  are  re- 
quired, may  be  cones  or  chambers  of  the  same  materials  or  of 
paper,  etc. 

Calomel,  mercuric  chloride,  iodine,  mercuric  sulphide,  arsenous 
oxide,  ammonium  chloride,  ammonium  carbonate,  and  certain 
other  substances  may  be  prepared  or  purified  by  sublimation. 

In  the  separation  of  volatile  solids  from  fixed  solids  by  means 


22  DRY    CHEMICAL    PROCESSES. 

of  heat,  the  volatile  substance  may  be  an  impurity  which  it  may 
or  may  not  be  worth  while  to  collect  by  condensation,  or  the  vola- 
tile substance  may  be  the  chief  product  and  the  fixed  substances 
impurities. 

The  condensed  volatile  solid  is  called  a  sublimate. 

In  processes  of  sublimation  the  condenser  is  usually  closer  to  the 
vessel  in  which  the  vapor  is  produced  than  is  the  case  in  distilla- 
tion, because  the  difference  between  the  temperature  to  which  the 
vapor  is  heated  and  that  at  which  it  is  condensed  is  not  great. 

The  sublimate  may  be  in  the  form  of  fine  powder,  as  in  the 
case  of  calomel,  or  in  large  aggregated  crystals  or  crystalline 
masses,  as  in  corrosive  sublimate,  or  in  large  amorphous  masses, 
as  in  arsenous  acid  when  manufactured  on  a  large  scale. 

When  the  sublimate  must  be  in  a  finely  divided  condition  the 
vessel  in  which  the  vapor  is  formed  must  be  kept  at  a  sufficiently 
high  temperature  in  every  part  to  prevent  any  condensation  of 
the  vapor  before  it  passes  into  the  condenser,  and  the  condenser 
must  be  cooled  considerably  below  that  temperature. 

But  when  large  masses  of  sublimate  (whether  crystalline  or 
amorphous)  are  desired,  the  condensation  must  be  effected  at  a 
temperature  but  little  lower  than  that  of  the  vaporization  of  the 
solid,  and  in  such  cases  the  product  is  frequently  collected  in  the 
upper  part  of  the  same  vessel  in  which  the  vapor  is  produced, 
or  the  whole  apparatus,  including  connecting  tube  and  condenser, 
must  be  kept  hot  enough  to  insure  the  desired  result. 

When  a  flask  or  retort  is  employed  for  the  vaporization  it  is 
necessary  to  guard  against  "choking"  caused  by  the  accumulation 
of  sublimate  in  the  neck  whereby  this  may  be  nearly  or  quite 
closed.  The  neck  must,  therefore,  in  all  processes  of  sublima- 
tion, be  quite  short,  and  in  some  cases  it  must  be  occasionally 
freed  from  sublimate  by  raking  the  latter  out. 

In  some  cases  it  is  the  best  plan,  when  the  quantities  operated 
upon  are  not  too  large,  to  use  tall  enough  cylindrical  vessels  of 
suitable  material,  vaporizing  the  solid  at  the  bottom  of  the 
cylinders  and  letting  the  vapor  be  condensed  at  the  upper  end 
which  is  to  be  rather  loosely  closed  with  chalk  stoppers,  paper 
or  clean  cotton.  The  cylinders,  tubes,  or  cylindrical  wide- 
mouthed  bottles,  used  for  sublimation  are  generally  placed  in  an 
inclined  position. 

[The  student  may  make  a  few  preliminary  experiments  in  sub- 


DRY    CHEMICAL    PROCESSES.  23 

limation  by  operating  upon  very  small  quantities  (say,  about  0.50 
Gm.)  of  any  of  the  following  named  substances:  camphor,  ben- 
zoic  acid,  iodine,  calomel,  corrosive  sublimate,  mercuric  iodide, 
mercuric  sulphide,  ammonium  carbonate,  ammonium  chloride, 
arsenous  oxide.  Use  a  long  test-tube ;  place  the  substance  to  be 
sublimed  in  the  bottofn  of  the  tube ;  use  a  test-tube  holder  to  pre- 
vent burning  the  ringers ;  heat  the  lower  third  of  the  tube,  espe- 
cially at  the  bottom,  by  moving  it  up  and  down  in  the  flame  of  a 
Bunsen  burner  or  a  spirit  lamp,  and  let  the  sublimate  be  con- 
densed in  the  cooler  upper  end  of  the  tube.  If  arsenous  oxide, 
or  any  mercury  compound,  or  other  poisonous  substance  is  ex- 
perimented with,  care  must  be  taken  not  to  permit  the  escape  of 
the  poisonous  vapor  and  its  inhalation.] 


CHAPTER  IV. 

SOLUTION ITS  NATURE,  CAUSES  AND  EFFECTS. 

39.  Numerous  striking  phenomena  of  solution  are  familiar  to 
all.     Sugar,  salt,  washing  soda  and  many  other  solids  are  com- 
pletely liquefied  when  put  in  a  sufficient  quantity  of  water,  and 
the  result  in  each  case  is  a  perfectly  homogeneous  liquid. 

Pieces  of  camphor  when  put  in  alcohol  dissolve  in  that  liquid, 
yielding  a  uniform  solution  containing  no  visible  particles  of  the 
camphor. 

Metallic  iron  placed  in  hydrochloric  acid  disappears  as  iron 
and,  if  a  sufficient  quantity  of  acid  be  used,  a  liquid  is  obtained 
in  which  no  solid  particles  of  matter  are  visible. 

Rosin  is  taken  up  in  solution  by  oil  of  turpentine ;  glycerin 
dissolves  crystallized  carbolic  acid ;  hot  olive  oil  makes  a  perfect 
solution  with  wax ;  and  benzin  forms  with  lard  an  entirely  homo- 
geneous liquid. 

These  phenomena  of  the  solution  of  solids  in  liquids  are  more 
striking  than  solutions  of  liquids  in  each  other,  solutions  of  gases 
in  liquids,  and  other  instances  of  intimate  molecular  blending  of 
two  or  more  substances,  because  we  see  that  the  pieces  or  particles 
of  solids  gradually  dissolve  and  finally  disappear  in  the  liquid  or 
solvent. 

40.  We  know   further  that  many  solids   are  unaffected  by 
water  and  by  various  other  liquids. 

Marble  does  not  dissolve  in  water,  alcohol,  ether,  chloroform, 
benzin,  oils,  or  glycerin;  but  it  does  dissolve  in  hydrochloric 
acid,  in  nitric  acid,  and  in  vinegar.  Glass  is  insoluble  in  nearly 
all  liquids  except  hydrofluoric  acid  and  strong  alkali  solutions. 
Diamond  is  insoluble  in  all  liquids. 

41.  Zinc  chloride  dissolves  in  less  than  one-third  of  its  weight 
of  water;  potassium  hydroxide  in  about  one-half  of  its  weight; 
potassium  iodide  in  three-fourths   of  its  weight;   sodium  thio 
sulphate  in  two-thirds ;  Rochelle  salt  in  one  and  one-half  times  its 
weight  of  water ;  alum  in  nine  times  its  weight ;  baking  "soda 
requires  nearly  twelve  times  its  weight  of  water  to  dissolve  it; 

24 


SOLUTION — ITS    NATURE,    CAUSES    AND   EFFECTS.  25 

cream  of  tartar  over  two  hundred  times  ;  lead  iodide  two  thousand 
times ;  copper  sulphide  nearly  one  million ;  and  silver  bromide 
about  two  million  times  its  weight  of  water. 

Camphor  dissolves  in  about  one-third  its  weight  of  chloro- 
form ;  in  its  own  weight  of  alcohol ;  and  in  from  fifteen  hundred 
to  two  thousand  times  its  weight  of  water. 

42.  Lixiviation  is  a  term  applied  to  the  separation  of  soluble 
inorganic  solids  from  insoluble  solid  matter  by  the  aid  of  water. 

Potassium  carbonate  is  "leeched"  out  from  wood  ashes,  and 
acid  calcium  phosphate  from  a  mixture  made  of  bone-ash  and 
sulphuric  acid,  by  passing  water  through  the  mixed  matter.  This 
process,  it  will  be  seen,  is  somewhat  analogous  to  percolation  or 
to  circulatory  displacement,  according  to  the  manner  in  which 
it  is  effected.  But  lixiviation  may  also  be  effected  by  maceration 
or  digestion  of  the  solid  matter  with  water,  the  solution  formed 
being  then  separated  from  the  residue  either  by  decantation  or  by 
straining  or  filtration. 

43.  Turning  now  to  the  solvent  action  of  liquids  upon  each 
other  we  find  that  comparatively  few  liquids  can  be  mixed  with 
each  other  in  all  proportions  to  form  permanent,  homogeneous, 
clear  solutions,  and  that  some  pairs  of  liquids  can  not  be  mixed 
in  any  proportions  to  form  such  solutions. 

Alcohol  and  water,  water  and  glycerin,  alcohol  and  glycerin, 
alcohol  and  ether,  ether  and  chloroform,  and  volatile  and  fixed 
oils,  form  perfect  solutions  in  all  proportions;  but  water  is  not 
soluble  in  fixed  oils,  nor  any  fixed  oil  in  water. 

Water  dissolves  ten  per  cent  of  its  weight  of  ether,  ether  dis- 
solves three  per  cent  of  its  weight  of  water,  and  these  two  dif- 
ferent solutions — the  solution  of  ether  in  water  and  the  solution 
of  water  in  ether — are  not  miscible  with  each  other  or  soluble  in 
each  other. 

Phenol  dissolves  in  about  fifteen  times  its  weight  of  water,  and 
water  is  soluble  in  about  twelve  to  thirteen  times  its  weight  of 
phenol ;  both  solutions  are  clear  and  permanent  at  the  ordinary 
room  temperatures,  but  they  are  immiscible  with  each  other.  At 
80°  C,  however,  phenol  and  water  are  miscible  with  each  other 
in  all  proportions,  forming  clear  homogeneous  solutions. 

Valeric  acid  is  soluble  in  thirty  parts  of  water,  and  water  is 
soluble  in  five  parts  of  valeric  acid ;  these  solutions  do  not  dis- 
solve each  other. 


26  SOLUTION ITS    NATURE,    CAUSES    AND   EFFECTS. 

But  any  two  liquids  which  dissolve  each  other  in  certain 
definite  proportions  hut  not  in  all  proportions  can  be  combined 
into  perfect  homogeneous  solutions  by  the  addition  of  a  third 
liquid  miscible  in  all  proportions  with  each  of  the  other  two. 

44.  Solutions  of  gases  in  liquids  are  also  formed.     In  fact,  all 
gases  are  soluble  to  some  extent  in  all  liquids,  although  it  often 
happens  that  the  gas  dissolves  in  the  liquid  so  sparingly  as  to 
be  regarded  as  practically  insoluble. 

One  volume  of  water  dissolves  about  1.8  volumes  of  carbon 
dioxide ;  4.3  volumes  of  hydrogen  sulphide ;  79.8  volumes  of  sul- 
phur dioxide ;  503  volumes  of  hydrochloric  acid ;  1050  volumes  of 
ammonia. 

Any  given  volume  of  any  given  liquid  dissolves  a  given  number 
of  volumes  of  any  given  gas  at  any  given  temperature  without 
regard  to  the  pressure.  Thus  one  volume  of  water  dissolves  1.8 
volumes  of  carbon  dioxide  not  only  at  the  ordinary  atmospheric 
pressure,  but  also  under  twice  that  pressure,  or  three  or  any 
other  number  of  times  that  pressure;  but  1.8  volumes  of  carbon 
dioxide  under  the  pressure  of  two  atmospheres  weighs  twice  as 
much  or  is  twice  as  large  a  quantity  of  carbon  dioxide  as  the 
same  number  of  volumes  of  that  gas  under  the  pressure  of  one 
atmosphere. 

45.  For  the  purposes  of  this  book  we  shall  adhere  to  the 
generally  recognized  definition  of  solution:    the  liquefaction  of 
any  substance  by  the  action  upon  it  of  any  liquid,  the  product 
being  a  homogeneous  clear  liquid  made  up  of  all  of  the  liquid 
used  as  a  solvent  and  all  of  the  substance  dissolved  in  it. 

This  definition  recognizes  no  solvent  except  a  liquid  solvent, 
and  no  solution  except  a  liquid  solution. 

But  in  a  more  general  sense  we  have  also  solutions  of  gases 
in  other  gases,  solutions  of  gases  and  solids  in  each  other,  and 
products  of  the  process  of  solution  which  are  not  liquid.  The 
evaporation  of  a  liquid  into  the  air  may  be  looked  upon  as  a 
solution  of  the  liquid  in  the  gases  of  which  the  air  consists. 

46.  A  real  or  perfect  solution  is,  accordingly,  for  the  purposes 
of  practical  pharmacy  and  pharmaceutical  chemistry,  a  perfectly 
homogeneous    and    clear    liquid    consisting    of    one    substance 
originally   in   liquid   form   recognized   as   the   solvent,   and   one 
or  more  other  substances  which  may  have  been,  previously  to  their 


SOLUTION ITS    NATURE,    CAUSES    AND   EFFECTS.  27 

solution,  either  solid,  liquid,  or  gaseous,  but  which  are  contained 
in  the  solution  in  a  liquid  form. 

47.  Solutions  can,   in  many  cases,  be   separated  again   into 
their  original  constituents.     Thus  a  solution  of  salt  in  water  can 
be  boiled  down  to  dryness,  the  water  being  thus  eliminated  by 
vaporization,  leaving  the  whole  quantity  of  the  salt  in  its  original 
solid  state  and  with  its  characteristic  properties  unchanged. 

Water  can  also  be  at  least  partially  separated  from  solutions  by 
freezing,  for  only  the  water  enters  into  the  formation  of  the  ice. 

A  solution  made  of  glycerin  and  alcohol  can  be  separated  into 
its  original  components  by  distilling  it,  the  volatile  alcohol  form- 
ing the  distillate  while  the  non-volatile  glycerin  remains  in  the 
still  or  flask.  A  solution  of  ammonia  in  water  can  be  more  or 
less  completely  separated  into  H3N  and  H2O  by  heating  it 
whereby  the  ammonia  is  expelled. 

But  when  iron  is  dissolved  in  hydrochloric  acid,  or  zinc  in  sul- 
phuric acid,  the  metal  can  not  be  recovered  from  the  solution,  nor 
the  acid  separated  from  it,  by  any  such  simple  means,  because 
these  solutions  do  not  consist  of  the  original  materials  put  to- 
gether, but  of  different  substances  formed  by  chemical  reaction 
between  the  original  substances. 

48.  Simple   solution   is   to   be   distinguished    from    chemical 
solution  by  the  fact  that  in  simple  solution  the  original  molecules 
of  the  solvent  and  dissolved  matter  remain  unaltered  and  no  new 
molecules  are  formed,  while 

Chemical  solution  results  in  the  formation  of  new  molecules 
which  take  the  place  of  the  original  substances. 

It  is  self-evident,  however,  that  chemical  solution  is  a  chemical 
reaction  in  which  one  of  the  factors  is  a  liquid  and  resulting  in 
products  which  form  together  a  homogeneous  liquid  by  solution. 
In  other  words,  chemical  solution  is  simple  solution  preceded 
by  a  chemical  reaction  between  factors  of  which  one  is  a  liquid. 

Examples  of  simple  solution  are  very  numerous  for  nearly  all 
solutions  in  which  water,  alcohol,  a  volatile  oil,  or  a  hydrocarbon 
is  the  solvent,  are  simple  solutions. 

Among  the  most  common  examples  of  chemical  solution  are: 
the  solution  of  metals,  metallic  oxides  and  hydroxides,  a,nd  other 
metallic  compounds,  in  acids,  the  solution  of  bromine  or  iodine, 
or  sulphur,  in  alkali  solutions ;  the  solution  of  iron  and  bromine, 
or  of  iron  and  iodine,  together,  in  water;  the  official  processes 


28  SOLUTION ITS    NATURE,    CAUSES    AND   EFFECTS. 

for  the  preparation  of  solution  of  potassium  arsenite,  solution  of 
subacetate  of  lead,  etc. 

49.  Simple  solvents,  or  neutral  solvents,  are  liquids  which  dis- 
solve soluble  substances  without  chemical  change. 

Chemical  solvents  are  liquids  which  dissolve  substances  by  trans- 
forming them  into  new  and  different  substances,  the  original 
molecules  of  both  solvent  and  dissolved  matter  disappearing. 

50.  Solution  is  caused  by  some  form  of  molecular  attraction. 
It  is  generally  ascribed  to  adhesion — the  attraction  between  unlike 
molecules. 

51.  Mendeleeff  describes  solutions  as  "fluid,  unstable,  definite 
chemical  compounds  in  a  state  of  dissociation."    He  says  "the  con- 
ception of  solutions  as  liquid  dissociated  definite  chemical  com- 
pounds is  based  on  the  following  considerations  :     ( i )  that  there 
exist  certain  undoubtedly  definite  chemical  crystalline  compounds 
(such  as   H2SO4.H2O,  or  NaCl.ioH2O,  or   CaCl2.6H2O,  etc.) 
which  melt  on  a  certain  rise  of  temperature,  and  then  form  real 
solutions  [see  Par.  52]  ;    (2)    that   metallic   alloys   in   a   molten 
condition  are  real  solutions,  but  on  cooling  they  often  give  entirely 
distinct  and  definite  crystalline  compounds,  which  are  recognized 
by  the  properties  of  alloys;   (3)   that  between  the  solvent  and 
the  substance  dissolved  there  are  formed,  in  a  number  of  cases, 
many  undoubtedly  definite  compounds,  such  as  compounds  with 
water  of  crystallization;  (4)  that  the  physical  properties  of  solu- 
tions, and  especially  their  specific  gravities  (which  are  very  ac- 
curately observable)  vary  with  a  change  in  composition,  and  in 
such  a  manner  as  the  formation  of  one  or  several  definite  but 
dissociating  compounds  would  require.     Thus,  for  example,  on 
adding  water  to  fuming  sulphuric  acid  its  density  is  observed 
to  decrease  until  it  attains  the  definite  composition  H2SO4,  or 
SO3-i-H2O   [see  Par.  55],    when  the  specific  gravity  increases, 
although  on  further  diluting  with  water  it  again  falls." 

"The  two  aspects  of  solution  above  mentioned,  and  the  hypo- 
theses which  have  as  yet  been  applied  to  the  examination  of  solu- 
tions, although  they  have  partially  different  starting  points,  yet 
will  doubtless  in  time  lead  to  a  general  theory  of  solutions,  be- 
cause the  same  common  laws  govern  both  physical  and  chemical 
phenomena,  inasmuch  as  the  properties  and  movements  of  mole- 
cules, which  determine  physical  properties,  are  dependent  on  the 


SOLUTION ITS    NATURE,    CAUSES   AND   EFFECTS.  2Q 

movements  and  properties  of  the  atoms,  which  determine  chemi- 
cal mutual  actions." 

52.  The  student  is  advised  to  hold  fast  to  the  distinction  be- 
tween physical  and  chemical  phenomena  as  indicated  in  the  fore- 
going statement,  and  to  the  difference  between  a  molecule  con- 
sisting of  atoms  united  to  each  other  by  one  complete  system  of 
atomic  linking  in  harmony  with  the  doctrines  of  polarity  and 
valence,  and  a  combination  of  unlike  molecules  held  together  by 
some  form  of  molecular  attraction  evidently  independent  of  the 
laws  of  polarity  and  valence.     Every  molecule  has  its  own  (and 
only  one)  unbroken  system  of  atomic  linking  whereby  all  of  its 
atoms  are  held  together  as  one  united  whole ;  but  in  such  a  com- 
pound as  CaCl2.6H2O  it  is  impossible  to  discover  any  link  or 
links  between  any  atom  or  atoms  of  the  CaCl2  on  the  one  hand 
and  any  atom  or  atoms  of  the  6H2O  on  the  other,  so  that  the 
CaCl2  and  6H2O  must  be  held  to  each  other  by  a  molecular  force 
quite  different  from  the  atomic  attraction  which  makes  the  mole- 
cule of  CaCl2  a  distinct  system  of  atomic  linking  and  each  mole- 
cule of  H2O  another  and  equally  independent  system. 

Moreover  the  student  must  remember  that  a  salt  combined 
with  the  water  called  "water  of  hydration"  and  that  called  "water 
of  crystallization"  does  not  differ  essentially  in  its  chemical  prop- 
erties from  the  anhydrous  salt,  and  that  a  dilute  water-solution 
of  any  salt  is  absolutely,  identical  with  any  other  equally  dilute 
water-solution  of  the  same  salt,  whether  the  kind  of  salt  used  to 
make  the  solution  be  the  anhydrous  salt  or  the  salt  containing  a 
maximum  or  a  minimum  amount  of  water  of  crystallization. 
Water-solutions  of  sodium  carbonate,  all  of  them  absolutely 
identical  as  to  strength,  composition,  and  every  property,  can  be 
made  out  of  either  Na2CO3,  or  Na2CO..H2O,  or  Na2CO3.sH2O, 
or  Na2CO37H2O,  or  Na2CO:{.ioH2O,  or  Na2CO3.i5H2O. 

53.  All  water-solutions  contain  water  as  water. 

54.  Deliquescence    indicates    a   molecular   attraction    of   the 
deliquescent  body  for  water,  resulting  in  the  formation  of  that 
kind  of  a  combination  or  union  (of  the  water  and  the  deliquescent 
body)  which  we  call  a  solution. 

55.  But  when  water  is  added  to  SO3  the  result  is  not  a  simple 
solution,  but  a  chemical  solution,  for  H2SO4  is  formed,  which  Is 
not 


3O  SOLUTION ITS    NATURE,    CAUSES    AND   EFFECTS. 

S=0  with  H— O— H,  but 


O 
H-O-L 


O— H. 


And  when  H2SO4  is  brought  into  contact  with  another  mole- 
cule of  water  the  resulting  product  is  not  a  solution  of  H2SO4 
in  water,  but  the  chemical  compound 

H— O, 

Hl-cte8^0  or  H*so" 

H-CT 

which  contains  no  water. 

If  still  another  molecule  of  water  be  added,  the  compound 
H6SO6  is  formed.  This,  too,  is  a  true  chemical  compound,  or 
complete  system  of  atomic  linking,  and  not  a  solution  since  it 
contains  only  one  kind  of  molecules. 

56.  We  know  that  some  substances  are  soluble  and  others 
insoluble  in  the  same  solvent;  that  different  soluble  substances 
differ  widely  in  their  respective  ratios  of  solubility  in  the  same 
solvent ;  and  that  a  substance  may  be  freely  soluble  in  one  solvent, 
moderately  soluble  in  another,  sparingly  soluble  in  a  third,  and 
quite  insoluble  in  a  fourth  solvent.     We  also  know  that  any  given 
solvent  dissolves  the  same  quantity  of  any  given  substance  under 
the  same  conditions.     But  the  law  which  must  specially  govern 
solution  and  solubilities  is  not  yet  understood. 

57.  That  molecular  attraction  of  some  kind  has  to  do  with 
solution  may  be  seen  from  the  phenomenon  of  deliquescence ; 
from  the  fact  that  a  contraction  of  volume  takes  place  when  mis- 
cible  liquids  are  united   into  solutions ;    from  the  upward  dif- 
fusion of  a  heavy  salt  in  water-solution  through  superincumbent 
pure  water ;  from  the  fact  that  when  a  water-solution  of  a  gas 
is  heated  it  sometimes  happens  that  water  alone  is  first  evapor- 
ated until  the  solution  acquires  a  certain  degree  of  concentration, 
after  which  this  solution,  containing  a  definite  proportion  of  the 


SOLUTION ITS    NATURE,    CAUSES    AND   EFFECTS.  3! 

gaseous    substance,    evaporates  without  further  separation ;   and 
from  other  facts. 

The  well  known  fact  that  HC1  can  not  be  evaporated  off  from 
its  water  solution  proves  that  the  HC1  and  H2O  are  held  to- 
gether strongly;  but  it  does  not  prove  that  they  are  chemically 
combined  (by  any  atomic  linking). 

58.  Ostwald  supports  the  conclusion  that  salts  in  water-solu- 
tion are  separated  into  simpler  constituents.     He  calls  attention 
to  the  fact  that  aqueous  solutions  of  salts  and  aqueous  solutions 
of  the  stronger  acids  and  bases,  all  of  which  he  calls  salt-solu- 
tions for  the  sake  of  brevity,  ''behave  as  if  they  contained  a  greater 
number  of  molecules  than  corresponds  with  the  formulae  of  the 
dissolved  salts."     From  these  considerations,  and  from  the  facts 
of  electrolysis,  he  concludes  that  salt-solutions  contain  parts  of 
the  molecules,  or  the  ions,  of  the  salts.     This  is  in  agreement 
with  MendeleefFs  definition  of  solutions  (51).     [See  also  Chap- 
ter VI.,  Par.  131,  Vol.  L] 

59.  The  velocity  of  reactions  occurring  in  solutions  may  be  at 
once  understood  upon  the  theory  that  the  reagents  are  in  a  state 
of  dissociation  into  their  respective  ions  or  radicals. 

60.  The  divisibility  of  matter  is  most  strikingly  illustrated  by 
the  color  reactions  which  may  be  produced  in  certain  extremely 
dilute  solutions,  and  Ostwald  points  out  that  elemental  radicals 
or  ions  present  in  a  solution  behave  quite  differently  from  the 
compound  radicals  or  ions  containing  the  same  elements.     Thus 
the  negative  ion  of  a  chloride,  Cl,  behaves  differently  from  the 
negative  ion  C1O4  of  the  perchlorates ;  the  negative  ion,  S,  of 
the  sulphides  produces  reactions  quite  different  from  those  pro- 
duced by  SO4 ;  and  the  positive  ion  Co  of  cobalt  salts  behaves  dif- 
ferently from  the  negative  ion  Co(CN)6. 

61.  ''The  colors  of  salt-solutions  are  essentially  the  colors  of 
the   ions  contained  therein"  (Ostwald). 

Very  dilute  solutions  of  cupric  chloride  (containing  little  of  the 
undissociated  compound  but  many  free  copper  ions)  are  blue; 
but  concentrated  solutions  of  the  same  compound  are  green  (be- 
cause they  contain  fewer  copper  ions  and  much  undissociated 
cupric  chloride).  This  and  other  examples  are  mentioned  to 
show  that  the  color  of  a  solution  is  sometimes  due  to  free  ions  and 
sometimes  to  the  undecomposed  compound.  A  solution  of 
chromic  anhydride  does  not  contain  H2CrO4,  for,  if  it  did,  the 


32  SOLUTION ITS    NATURE,    CAUSES    AND   EFFECTS. 

ions  of  CrO4  would  make  it  yellow ;  but  it  does  contain  H2Cr2O7 
and  is,  therefore,  colored  red  by  the  ion  Cr2O7. 

An  interesting  example  not  mentioned  in  Ostwald's  book  is 
that  presented  by  ferrous  and  ferric  salts.  If  ferrous  chloride 
and  ferric  chloride  are  dissociated  into  their  respective  ions  by 
solution  it  must  be  admitted  that  the  ions  of  both  chlorides  are 
Fe  and  Cl ;  but  the  green  solution  of  ferrous  chloride  contains 
diad  ferrous  ions  while  the  reddish-brown  solution  of  ferric 
chloride  contains  triad  ferric  ions.  It  is  true  that  the  difference 
between  ferrous  iron  and  ferric  iron  is  known  only  from  their 
compounds,  and  that  ferrous  iron  can  be  oxidized  to  ferric  and 
ferric  iron  reduced  to  ferrous,  so  that  the  distinction  between 
diad  iron  and  triad  iron  must  depend  upon  their  respective  units 
of  combining  value  actually  used  (their  respective  polarity- 
values)  ;  but  the  dissociated  ferrous  and  ferric  ions  in  solutions 
must  still  be  respectively  bivalent  and  trivalent  since  the  removal 
of  any  ion  from  the  solution  can  not  be  admitted. 

The  color  may  depend  on  either  positive  or  negative  ions. 
If  it  be  admitted  that  iron  salts  are  in  a  state  of  partial  dissociation 
when  in  water-solution,  and  that  "the  colors  of  salt  solutions  are 
essentially  the  colors  of  the  ions  contained  therein,"  then  the  solu- 
tions of  ferrous  salts  are  colored  green  by  the  ions  of  diad  or 
ferrous  iron,  while  the  solutions  of  ferric  salts  are  colored  red- 
dish-brown by  the  ions  of  triad  or  ferric  iron.  Yet,  ferrous  iron 
and  ferric  iron  are  both  commonly  regarded  as  single  atoms. 

[Ferrous  and  ferric  salts  in  the  dry  state  are  generally  nearly 
white  or  very  pale,  but  they  exhibit  a  decided  color  as  soon  as 
dissolved  in  water.  Other  anhydrous  salts  also  exhibit  different 
colors  when  dissolved  in  water.] 

62.  Only  acids,  bases  and  salts  are  believed  to  undergo  dis- 
sociation in  their  water-solutions.  If  this  be  true  there  are 
numerous  substances  which  form  solutions  without  dissociation. 
Moreover,  the  compounds  which  become  separated  into  their  ions 
by  solution  in  water  may  dissolve  in  other  liquids  without 
dissociation,  strong  solutions  may  contain  no  free  ions,  while 
weaker  solutions  of  the  same  salt  give  evidence  of  partial  disso- 
ciation ;  and  complete  dissociation  is  not  believed  to  be  effected 
except  in  infinitely  dilute  solutions. 


CHAPTER  V. 

SOLVENTS SOLUBILITY SOLUTIONS. 

63.  Common  solvents.     The  most  common  simple  solvents  for 
inorganic  substances  include  water,  alcohol,  glycerin  and  acetic 
acid. 

Water  is  the  most  important  of  all  solvents,  and  its  value  is 
mainly  due  to  the  fact  that  it  is  chemically  indifferent  with  rela- 
tion to  most  other  substances.  Accepting  the  conclusion  recently 
advanced  that  water,  when  used  as  a  solvent,  causes  the  partial 
dissociation  of  certain  classes  of  water-soluble  compounds  into 
their  respective  ions,  we  must  at  the  same  time  remember  that 
the  water  itself  remains  undissociated.  Water  thus  facilitates 
chemical  reactions  when  solutions  containing  the  reagents  are 
mixed,  and  it  is  probable  that  medicinal  substances  in  water-solu- 
tion must  act  more  promptly  and  energetically  whenever  they 
are  in  a  state  of  partial  dissociation. 

Water  dissolves  a  large  number  of  inorganic  compounds  and 
also  numerous  organic  substances.  But  many  substances  which 
may  long  remain  unaltered  when  in  solution  in  alcohol,  ether, 
glycerin,  and  certain  other  solvents,  are  liable  to  more  or  less  rapid 
decomposition  when  kept  in  water-solution. 

Alcohol  is  an  exceedingly  valuable  pharmaceutical  solvent,  be- 
cause, like  water,  it  is  generally  chemically  neutral,  it  dissolves 
and  extracts  from  plant  drugs  most  of  the  constituents  that  pos- 
sess medicinal  activity,  and  the  solutions  it  forms  are  far  more 
permanent  than  water-solutions.  Alcohol,  however,  dissolves 
comparatively  few  inorganic  compounds. 

Glycerin  dissolves  perhaps  all  water-soluble  substances  and 
many  other  substances  besides.  Glycerin  dissolves  normal  bis- 
muth nitrate  without  decomposing  it.  Glacial  acetic  acid  also 
dissolves  normal  bismuth  nitrate. 

64.  The  term  solubility  when  mentioned  without  naming  the 
solvent    means    the   maximum    solubility   in    water   at    ordinary 
room  temperatures. 

The  ratio  or  extent  of  the  solubility  of  any  one  substance  in 

33 
Vol.  II— 3 


34  SOLVENTS SOLUBILITY SOLUTIONS. 

different  liquids,  and  of  different  substances  in  the  same  liquid, 
may  range  all  the  way  from  absolute  insolubility  to  unlimited 
solubility.  Flint  is  absolutely  insoluble  in  water  and  all  other 
simple  solvents ;  but  a  solution  of  ferric  citrate  may  be  evaporated 
to  complete  dryness  without  any  separation  of  the  salt  from  it. 

65.  The  relation  of  the  solubility  of  a  substance  to  its  chemical 
composition  is  not  understood.     Hence  the  chemical  composition 
does  not  furnish  a  reliable  or  consistent  guide  to  solubility,  for 
there  are  many  apparent  exceptions  or  inconsistencies. 

Thus,  while  the  halides  of  the  three  common  alkali  metals  are 
all  readily  water-soluble  and  those  of  lithium  more  soluble  than 
those  of  sodium  and  potassium,  their  hydroxides  and  carbonates 
stand  in  the  opposite  order.  Of  the  halides  of  calcium,  strontium 
and  barium,  those  of  calcium  are  most  freely  soluble  and  those 
of  barium  least  so,  which  would  seem  to  agree  with  the  order  in 
which  the  halides  of  the  alkali  metals  stand  to  each  other,  the 
metal  having  the  smallest  atomic  weight  forming  the  most  readily 
soluble  halide.  But,  on  the  other  hand,  lead  iodide  is  far  more 
readily  soluble  than  mercuric  iodide,  while  mercuric  chloride  is 
far  more  soluble  than  lead  chloride.  The  nitrates  of  copper,  sil- 
ver and  lead  are  all  very  readily  soluble ;  but  while  copper  sul- 
phate dissolves  in  2.6  parts  of  water,  silver  sulphate  requires  200 
parts  of  water  for  its  solution  and  lead  sulphate  32,000  parts. 

Sodium  dichromate  is  more  soluble  than  sodium  chromate ;  but 
potassium  dichromate  is  less  soluble  than  potassium  chromate. 

Borax  is  soluble  in  16  parts  of  water,  and  cream  of  tartar  in 
201  parts;  but  the  two  substances  together  dissolve  in  a  very 
small  amount  of  water  to  form  "borax-tartar"  or  potassium-so- 
dium boro-tartrate  which  is  soluble  in  water  without  any  limit, 
being  deliquescent. 

66.  The  ratio  of  solubility  of  a  substance  may  be  materially 
affected  by   its   condition.     A   hydrous   substance  is   frequently 
more  soluble  than  the  anhydrous;  the  amorphous  substance  may 
be  more  or  less  readily  soluble  than  the  crystallized ;  a  substance 
containing  more  water  of  crystallization  is  usually  more  readily 
soluble  than  the  same  substance  with  a  less  percentage  of  water ; 
a   recently   prepared   chemical   compound  may  be  more  or  less 
readily  soluble  than  the  same  substance  after  it  has  been  kept  a 
long  time;  dry  heat  (as,  for  instance,  fusion)  may  also  affect  the 


SOLVENTS SOLUBILITY SOLUTION  S.  35 

solubility  of  a  solid ;  and  solubility  may  further  be  affected  by 
contact  with  other  substances. 

Crystallized  A1(OH)3  is  difficultly  soluble  in  acids,  while  a 
freshly  precipitated  amorphous  A1(OH)3  is  easily  soluble  in 
acids  but  gradually  loses  its  solubility  when  kept. 

67.  The  presence  of  one  substance  in  a  solution  may  very 
greatly  affect  the   solubility  of  another   substance  in  the  same 
liquid.     Thus   water-soluble  potassium   salts   are   frequently  in- 
soluble in  saturated  solutions  of  ammonium  salts ;  potassium  sul- 
phate is  insoluble  in  a  saturated  solution  of  ammonium  sulphate, 
potassium  nitrate  in  a  saturated  solution  of  ammonium  nitrate, 
and  potassium  carbonate  in  strong  ammonia  water.     Potassium 
sulphate  is  insoluble  in  a  saturated  solution  of  potassium  carbon- 
ate, and  potassium  hydroxide  in  a  solution  of  calcium  hydroxide. 

The  total  displacement  of  one  salt  from  its  solution  by  the 
addition  of  another  salt  can  sometimes  be  effected. 

68.  Organic  substances  which  are  soluble  in  water  are  fre- 
quently found  to  be  nearly  or  quite  insoluble  in  strong  water- 
solutions  of  inorganic  substances.     Thus  water-soluble  salts  of 
the  alkaloids  are  generally  insoluble  in  concentrated  water-solu- 
tions of  metallic  salts ;  pepsin,  soap,  and  various  other  substances 
can  be  precipitated  from  their  solutions  by  metallic  salts. 

69.  On  the  other  hand  it  happens  sometimes  that  the  pres- 
ence of  one  substance  in  a  solution  aids  the  solution  of  another 
substance  in  the  same  liquid,  as  when  ammonium  chloride  facili- 
tates the  solution  of  mercuric  chloride. 

70.  Mixed  solvents.     When  two  or  more  solids  are  dissolved 
in  a  mixture  of  two  or  more  liquids  a  separation  into  distinct  lay- 
ers is  sometimes  the  result. 

Although  alcohol  and  water  are  miscible  in  all  proportions  they 
are  sometimes  separated  from  each  other  on  the  addition  of  inor- 
ganic salts  soluble  in  water  and  organic  substances  soluble  in 
alcohol,  so  that  an  aqueous  solution  of  the  inorganic  salt  and  an 
alcoholic  solution  of  the  organic  compound  form  separate  layers. 

But  certain  single  inorganic  salts  may  also  cause  the  partial 
separation  of  mixed  solvents  by  forming  a  separate  solution  with 
each.  Hydroalcoholic  solutions  of  manganese  sulphate,  and  also 
of  potassium  carbonate,  may  separate  into  two  layers,  one  of 
which  is  a  concentrated  water-solution  containing  but  little 


36  SOLVENTS SOLUBILITY SOLUTION  S. 

alcohol,  while  the  other  layer  consists  chiefly  of  alcohol  contain- 
ing very  little  of  the  salt. 

71.  Immiscible  solvents.     Water  and  ether,  water  and  chloro- 
form, and  other  pairs  of  liquids  which  are  not  soluble  in  each 
other  in  all  proportions,  are  frequently  employed  for  the  purpose 
of  transferring  certain  substances  from  one  solvent  to  the  other, 
for    removing    a    dissolved  substance  from  its  solution,  and  for 
separating  different   substances  from  each  other.     A  substance 
dissolved  in  one  of  the  solvents  may  be  divided  between  it  and 
the  second  solvent,  or  it  may  be  almost  completely  washed  out  or 
withdrawn  from  its  original  solution. 

72.  The  partial  removal  of  the  solvent  from  a  solution  by  the 
addition  of  another  liquid  which  takes  up  the  solvent  with  more 
or  less  avidity  is  frequently  practicable.    Thus  water  may  be  par- 
tially withdrawn  from  a  strong  salt-solution  by  the  careful  addi- 
tion of  a  superincumbent  layer  of  strong  alcohol,  when  it  may 
happen  that  the  alcohol  gradually  becomes  diluted  and  the  salt 
is  partially  separated  by  crystallization  or  precipitation  from  its 
solution  for  want  of  sufficient  solvent. 

73.  By  the  term  physical  precipitation  we  mean  the  separation 
of  a  dissolved  substance  from  its  solution  by  the  addition  of  a 
non-solvent  liquid  miscible  with  the  solvent. 

Since  alcohol  and  water  are  miscible  with  each  other  and  many 
substances  which  are  soluble  in  one  of  these  liquids  are  insoluble 
in  the  other,  various  substances  in  water-solution  can  be  "thrown 
out  of  solution"  by  the  addition  of  alcohol,  and  many  other  sub- 
stances can  be,  in  a  similar  manner,  precipitated  from  their 
alcoholic  solutions  by  the  addition  of  water. 

A  saturated  solution  of  KC1  made  with  pure  water  at  15° 
contains  24.6  per  cent  of  the  chloride;  but  if  made  with  water 
mixed  with  10  per  cent  of  alcohol  the  saturated  solution  contains 
only  about  20  per  cent  of  the  chloride,  and  if  made  with  a  mix- 
ture of  equal  proportions  of  water  and  alcohol  it  contains  only 
about  5  per  cent  of  the  salt. 

A  saturated  solution  of  ferrous  sulphate  (FeH2SO5.6H2O) 
made  with  pure  water  contains  37.2  per  cent  of  the  salt  (at  15°)  ; 
but  a  saturated  solution  of  the  same  salt  made  with  a  mixture  of 
60  per  cent  of  water  and  40  per  cent  of  alcohol  contains  only  0.3 
per  cent  of  the  ferrous  sulphate. 

A  saturated  water-solution  of  copper  sulphate  at  15°  contains 


SOLVENTS — SOLUBILITY — SOLUTIONS.  37 

27.2  per  cent  of  the  salt;  but  a  saturated  solution  made  with  a 
mixture  of  60  per  cent  of  water  and  40  per  cent  of  alcohol  con- 
tains only  0.25  per  cent  of  copper  sulphate. 

74.  To  aid  solution  we  may  employ  such  means  as  will  bring 
the  solvent  into  intimate  contact  with  the  substance  to  be  dis- 
solved and  also  any  other  agencies  by  which  the  liquefaction  of 
that  substance  is  facilitated. 

To  facilitate  the  solution  of  a  solid  the  solid  substance  may  be 
crushed  or  powdered  in  order  to  expose  a  greater  surface  to 
the  action  of  the  solvent,  and  the  solid  and  solvent  may  be 
shaken  or  stirred  together  to  further  increase  the  freedom  of 


Fig.  14.  Solution  mortar  of  porcelain.  Fig.  15.  Perforated  porcelain  basket 

tor  dissolving  metals  in  acids  by 
circulatory  displacement. 

contact  between  them.  If  the  solid  should  rest  on  the  bottom  of 
the  vessel  in  which  the  solution  is  effected,  and  the  solvent  re- 
main at  rest  over  the  solid,  then  the  solution  first  formed  must 
cover  and  surround  the  solid  so  as  to  prevent  fresh  portions  of 
solvent  from  coming  in  contact  with  it;  but  agitation  serves  the 
purpose  of  distributing  the  solution  throughout  the  whole  body  of 
the  liquid. 

The  solid  may  be  placed  in  a  mortar  and  triturated  with  succes- 
sive portions  of  the  solvent,  each  strong  solution  thus  formed  be- 
ing poured  off  from  the  undissolved  remainder,  and  this  con- 
tinued until  all  of  the  solid  shall  have  been  dissolved.  By  this 
means  the  quantity  of  solvent  required  to  complete  the  solution 
may  be  reduced,  since  it  is  practicable  to  produce  a  practically 
saturated  solution  with  each  portion  of  solvent. 


38  SOLVENTS SOLUBILITY SOLUTIONS. 

Another  effective  method  is  that  called  circulatory  displacement, 
which  consists  in  placing  the  solid  substance  in  a  perforated  fun- 
nel, dish,  or  basket,  or  in  a  bag,  or  on  a  colander  or  perforated 
diaphragm,  just  below  the  surface  of  the  solvent,  so  that  the  solu- 
tion formed  may  at  once  descend  to  the  bottom  of  the  vessel,  per- 
mitting fresh  portions  of  solvent  to  freely  attack  the  undissolved 
remainder  of  the  solid  until  all  of  it  has  entered  into  solution. 

Heat  almost  always  facilitates  the  solution  of  solids  in  liquids 
because  the  heat  opposes  the  cohesion  which  holds  the  molecules 
of  the  solid  together. 

Solids  which  have  a  tendency  to  form  clots  or  agglutinations 
when  wetted  should  not  be  powdered  to  prepare  them  for  solu- 
tion. "Scale  salts"  of  iron  dissolve  much  more  readily  when  not 
crushed  or  powdered ;  resins,  when  dissolved  in  alcohol  or  in  vola- 
tile oils,  should  be  in  pieces  or  in  very  coarse  powder. 

Agitation,  cold  and  pressure  facilitate  the  solution  of  gases  in 
liquids. 

75.  A  contraction  of  volume  nearly  always  results  from  solu- 
tion, whether  the  substance  dissolved  be  a  solid,  a  liquid  or  a  gas. 
In  other  words,  the  volume  of  the  resultant  solution  is  nearly 
always  less  than  the  sum  of  the  original  volumes  of  the  solvent 
and  the  dissolved  matter.     But  the  volume  of  the  solution  is 
always  greater  than  the  volume  of  the  solvent  alone. 

When  49.836  volumes  of  water  and  53.939  volumes  of  absolute 
alcohol  are  mixed  the  total  103.775  volumes  contract  to  form  just 
100  volumes  (at  15°  C). 

76.  When  no  chemical  action  accompanies  the  process  of  solu- 
tion there  is  always  a  liberation  of  heat  attendant  upon  a  con- 
traction of  volume,  and  an  absorption  of  heat  attendant  upon  an 
expansion  of  volume  resulting  from  the  solution. 

77.  When  a  salt  containing  a  large  amount  of  water  of  crys- 
tallization is  dissolved  in  water  the  volume  of  the  solution  may 
exceed  the  sum  of  the  original  volumes  of  the  salt  and  the  water ; 
but  when  an  anhydrous  salt  capable  of  taking  up  much  water  of 
crystallization  is  dissolved  in  water  a  contraction  of  volume  may 
be  expected.    Contraction  of  volume  occasionally  takes  place  when 
a  concentrated  water-solution  of  a  salt  is  diluted  with  more  water. 

78.  Relations  of  heat  to  solution.     Reference  has  already  been 
made  to  the  liberation  of  heat  due  to  a  contraction  of  volume  in 
the  formation  of  solutions.     But  the  student  should  know  that 


SOLVENTS SOLUBILITY SOLUTIONS.  39 

the  rise  or  fall  of  temperature  attendant  upon  the  formation  of 
solutions  must  be  affected  also  by  various  other  influences.  As 
solids  must  take  up  latent  heat  when  they  become  liquefied  by 
solution,  it  frequently  happens  that  a  very  considerable  reduction 
of  temperature  results  when  a  readily  soluble  salt  is  dissolved 
in  water ;  and  as  any  gas  must  give  up  latent  heat  when  liquefied 
by  solution  the  temperature  of  the  water  in  which  the  gas  is  being 
dissolved  frequently  rises  perceptibly.  Besides,  there  may  be 
various  molecular  combinations  taking  place  in  the  formation  of 
solutions,  and  these  may  affect  the  temperature.  Finally,  chemi- 
cal reactions  also  cause  changes  of  the  temperature. 

When  17  Gm.  of  H3N  is  compressed  to  the  liquid  state  it  evolves 
4400  units  of  heat ;  but  when  it  dissolves  in  18  Gm.  of  water  the 
same  quantity  of  H3N  evolves  7535  heat  units.  The  3135  addi- 
tional heat  units  were  generated  by  the  chemical  reaction  by 
which  the  H3N  and  the  H2O  formed  H4NOH. 

When  30  parts  of  absolute  alcohol  is  mixed  with  70  parts  of 
water  the  temperature  rises  9.14  degrees,  which  is  not  accounted 
for  by  the  contraction  of  volume.  It  is  assumed  that  the  alcohol 
combines  in  some  way  with  a  certain  number  of  molecules  of 
water. 

When  ether  and  chloroform  are  mixed  in  equal  volumes  the 
temperature  rises  14.  °4- 

But  when  equal  volumes  of  alcohol  and  carbon  disulphide  are 
mixed  the  temperature  falls  5.°6. 

That  anhydrous  compounds  which  take  up  water  in  molecular 
combination  dissolve  in  water  with  evolution  of  heat  is  well 
known ;  but  there  are  many  examples  of  the  solution  of  solids  at- 
tended by  a  considerable  elevation  of  temperature  in  which  it  is 
not  known  what  compounds  are  formed,  if  any.  Great  evolution 
of  heat  attends  the  solution  of  KOH  in  water ;  but  potassium 
hydroxide  is  not  known  to  combine  with  water  to  form  any  defi- 
nite compound.  [No  system  of  atomic  linking  of  K,  O  and  H 
is  possible  except  KOH.] 

Anhydrous  calcium  chloride  takes  up  water  to  form  a  definite 
hydrate  and  this  hydration  is  attended  by  an  elevation  of  tem- 
perature; but  when  hydrous  calcium  chloride  is  dissolved  in 
water  the  temperature  falls. 

79.  Freezing  mixtures.  When  readily  water-soluble  salts  are 
put  in  a  comparatively  small  amount  of  water — say,  about  twice 


40  SOLVENTS — SOLUBILITY — SOLUTIONS. 

their  weight — the  temperature  of  the  water  is  greatly  depressed 
by  the  solution  of  the  salt.  The  temperature  may  be  reduced  as 
much  as  20°  by  various  salts. 

A  mixture  of  3  parts  of  crystallized  calcium  chloride  and  2 
parts  of  snow  will  cause  mercury  to  congeal. 

Two  parts  of  snow  or  crushed  ice  and  one  part  of  common 
salt  will  make  a  very  effective  freezing  mixture  for  ice-cream 
freezers  and  for  other  purposes. 

A  mixture  of  5  parts  of  ammonium  chloride  and  5  parts  of 
potassium  nitrate  with  19  parts  of  water  causes  a  fall  of  20°  in  the 
temperature  of  the  water. 

80.  Heat  generally  increases  the  solubility  of  solids  and  liquids. 
Boiling  water  frequently  dissolves  many  times  as  much  of  a 
metallic  salt  as  can  be  dissolved  in  cold  water ;  but  any  substance 
which  is  quite  insoluble  in'  cold  water  is  also  quite  insoluble  in 
hot  water. 

One  hundred  parts  of  boiling  water  will  hold  50  parts  of  potas- 
sium chlorate  in  solution ;  but  when  such  a  solution  is  allowed 
to  cool  to  about  15°  only  6  parts  of  the  salt  remain  in  solution 
while  the  remaining  44  parts  will  crystallize  out. 

Alum  is  soluble  in  less  than  one-third  its  weight  of  boiling 
water,  but  requires  nine  times  its  weight  of  water  at  15°  for  its 
solution. 

Borax  dissolves  in  one-half  its  own  weight  of  boiling  water, 
but  is  not  soluble  in  less  than  16  parts  of  water  at  15°. 

Eight  parts  of  water  at  15°  will  dissolve  no  more  sodium  car- 
bonate than  is  soluble  in  i  part  of  boiling  water. 

81.  The  increased  ratio  of  solubility  of  a  solid  in  water  caused 
by  a  rise  of  the  temperature  grows  more  rapidly  than  the  heat 
rises ;  but  the  increased  solubility  resulting  from  a  continued  ele- 
vation of  temperature  is  often  very  irregular. 

82.  Some  solids  do  not  dissolve  more  readily  in  hot  water 
than  in  cold  water.    This  is  true  of  acacia  and  some  other  soluble 
varieties  of  gum. 

Sodium  chloride  is  only  slightly  more  soluble  in  boiling  water 
than  in  water  at  15° ;  100  parts  of  water  at  o°  dissolves  35.7  parts 
of  NaCl,  36  parts  at  20°,  and  39.7  parts  at  100°. 

A  solution  of  calcium  hydroxide  made  saturated  at  15°  loses 
about  one-half  of  the  dissolved  hydroxide  on  being  boiled  (with- 
out contact  with  the  air). 


SOLVENTS — SOLUBILITY — SOLUTIONS.  4! 

83.  As  the  solubility  of  solids  is  materially  affected  by  the  pro- 
portion of  water  contained  in  them  as  water  of  crystallization  or 
water  of  hydration,  and  as  this  proportion  of  water  may  depend 
upon  the  temperature,  it  follows  that  unexpected  differences  are 
sometimes  attributable  to  these  facts.     It  is  stated  that  solutions 
of  sodium  sulphate  below  33°  contain  Na2SO4.ioH2O;  but -solu- 
tions of  the  same  salt  having  a  temperature  above  34°  contain 
Na2SO4.     Hence  sodium  sulphate  dissolves  in  about  one-fourth 
of  its  own  weight  of  water  at  33°  ;    but  its  solubility  decreases 
above  that  temperature  so  that  it  requires  nearly  one-half  its  own 
weight  of  water  at  100°  to  dissolve  it. 

84.  Supersaturated  solutions  are  solutions  which  at  any  given 
temperature  retain  a  larger  proportion  of  the  dissolved  substance 
than  the  solvent  is  capable  of  dissolving  at  that  temperature. 

We  have  seen  that  many  salts  are  more  soluble  in  water  at  a 
higher  temperature  than  at  a  lower  temperature.  Now,  if  a  sat- 
urated solution  of  such  a  salt  be  prepared  at  any  given  tempera- 
ture and  then  allowed  to  cool,  it  frequently  happens,  if  the  liquid 
remains  at  perfect  rest,  that  all  the  salt  remains  in  the  solution, 
at  least  for  a  time,  notwithstanding  the  reduction  of  temperature. 

If  a  saturated  solution  of  sodium  sulphate  be  made  at  34°  it 
will  contain  about  80  per  cent  of  the  salt  and  20  per  cent  of  water ; 
if  made  at  15°  the  saturated  solution  of  sodium  sulphate  will  con- 
sist of  about  26  per  cent  of  the  salt  and  74  per  cent  of  water.  Yet, 
a  solution  of  sodium  sulphate  saturated  at  34°  and  then  allowed  to 
cool  gradually  to  15°,  if  not  shaken  or  otherwise  disturbed,  will 
continue  to  retain  in  solution  80  per  cent  of  the  salt.  It  is  then  a 
supersaturated  solution. 

A  supersaturated  solution  of  the  salt  at  a  low  temperature  may, 
however,  be  but  a  saturated  solution  of  the  same  salt  with  a  dif- 
ferent proportion  of  water  of  crystallization. 

Hydrous  salts  generally  form  supersaturated  solutions  more 
readily  than  anhydrous  salts. 

Supersaturated  solutions  are  readily  formed  by  sodium  sul- 
phate, magnesium  sulphate,  the  alums,  and  sodium  thiosulphate. 

85.  Determination  of  the  solubility  of  solids.  The  solubility 
of  solids  in  water  or  in  alcohol  may  be  determined  by  two  prin- 
cipal methods:  I,  a  saturated  solution  may  be  prepared  at  any 
given  temperature  and  the  strength  of  this  solution  ascertained ; 
or  2,  a  saturated  solution  may  be  prepared  at  a  higher  tempera- 


42  SOLVENTS — SOLUBILITY — SOLUTIONS. 

ture,  the  solution  then  cooled  to  any  given  lower  temperature  at 
which  it  should  be  kept  for  a  day  or  two,  being  occasionally 
shaken,  and  its  strength  then  found.  The  results  obtained  by  the 
first  method  are  liable  to  be  somewhat  too  low,  and  those  obtained 
by  the  second  method  are  liable  to  be  too  high. 

86.  Solubilities  are  usually  stated  at  15°,  and  this  is  a  very  suit- 
able standard  temperature  for  the  expression  of  the  solubility  of 
solids,   because   saturated   solutions   prepared  at   15°   are  rarely 
exposed  to  any  lower  temperature,  the  average  temperature  of  the 
work  room  being  higher. 

87.  The  most  satisfactory  method  of  determining  the  solubility 
of  a  salt  in  water  at  15°  is  to  make  a  saturated  solution  at  about 
1 6°  to  20°  ;  to  set  this  solution  aside  for  24  hours  at  15°,  shaking 
it  occasionally ;  then  filter ;  then  evaporate  a  weighed  quantity  to 
dryness  and  weigh  the  residue. 

It  is,  of  course,  necessary  in  carrying  out  this  method  to  know 
precisely  what  the  residue  is  -  -  whether 
hydrous  or  anhydrous,  and  if  hydrous,  how 
much  water  it  contains,  etc.  The  result 
should  be  verified  by  analysis;  a  weighed 
quantity  of  the  salt  being  dissolved  in  a 
weighed  quantity  of  water  and  this  solution 
analyzed  quantitatively,  the  result  to  serve 
as  a  check  upon  the  composition  of  the 
salt,  and  also  upon  the  result  of  a  quantita- 

F1ng6soTitfoknsf°fnWdetger:      tive   analysis   of    the    saturated    solution, 
mmations  of  soiubiii-      which  should  also  be  performed.    In  other 

words,  the  salt  used  to  make  the  solution, 

the  saturated  solution  prepared  from  it,  and  the  residue  obtained 
upon  evaporating  a  given  weight  of  that  saturated  solution,  must 
all  be  titrated,  and  the  results  compared  with  the  weight  of  the 
residue.  If  the  salt  is  hydrous  the  residue  must  be  dried  at  a 
given  temperature  until  it  ceases  to  lose  weight,  and,  if  practi- 
cable, all  of  the  water  of  crystallization  or  any  other  water  con- 
tained in  it  should  be  expelled. 

88.  Dr.  Rice's  Lysimeter.     In  order  to  determine  the  rate  of 
solubility  of  a  substance  at  a  temperature  considerably  higher  than 
that  of  the  air  in  the  work  room,  and  to  obtain  a  filtered  solution 
of  the  same    temperature  as  that  at  which  the    solution    was 
saturated,  Dr.  Charles  Rice  devised  an  instrument  which. he  gave 


SOLVENTS SOLUBILITY SOLUTIONS.  43 

the  name  "lysimeter,"  which  is  here  described  and  shown  in  fig. 

The  lysimeter  consists  of  a  glass  tube,  a,  which  is  150  milli- 
meters long  and  10  millimeters  in  external  diameter,  provided  at 
one  end  with  a  well-fitting  glass-stopper,  c,  the  opposite  end  of 
the  tube  being  cup-shaped,  with  a  con- 
traction between  the  cup  and  the  body 
of  the  tube  as  shown  in  the  cut.  A 
ground  glass  bell,  e,  is  made  to  fit  into 
the  cup.  The  bottom  of  this  bell  is  per- 
forated as  shown  in  /.  The  ground 
glass  stopper,  b,  also  fits  into  the  cup, 
and  is  to  be  used  to  close  the  cup  after 
the  removal  of  the  bell. 

The  quantity  of  solution  must  be  suf- 
ficient so  that  at  least  one-half  of  the 
instrument  can  be  immersed  in  it.  The 
solution  may  be  made  and  contained  in 
a  glass  cylinder,  a  beaker,  or  a  wide 
test-tube.  The  use  of  the  lysimeter  may  b 
be  illustrated  by  an  example  as  follows, 
assuming  that  the  solubility  of  some  solid 
in  boiling  alcohol  is  to  be  determined :  The  stopper  c 
is  inserted  into  the  tube  a,  and  the  glass  bell  e  into 
the  cup-shaped  end  of  the  tube.  A  little  pledget  of 
pure  cotton  is  put  into  the  bell,  e,  and  held  in  place 
by  a  fine  platinum  wire  passing  around  the  contrac- 
tion or  neck  behind  the  cup  and  over  the  mouth  of 
the  bell.  A  sufficient  quantity  of  alcohol  is  put  in 
the  vessel  in  which  the  solution  is  to  be  made,  and 
heated  by  immersion  in  hot  water,  the  powdered 
solid  being  added  to  the  alcohol  in  sufficient  quan- 
tity to  produce  a  saturated  solution,  a  small  residue 
remaining  undissolved  after  continuing  the  boiling 
of  the  alcohol  long  enough.  The  lysimeter  is  now 
inserted,  prepared  as  described,  cup-shaped  end 
downwards,  and  when  the  instrument  has  assumed 
the  temperature  of  the  boiling  liquid,  the  stopper  c  is  removed. 
The  alcoholic  solution  then  enters  the  tube  through  the  cotton 
filter  in  the  cup.  To  insure  uniformity  of  the  solution  the  liquid 


44  SOLVENTS SOLUBILITY SOLUTIONS. 

may  be  allowed  to  flow  back  through  the  cotton  once  or  twice. 
The  stopper  c  is  now  replaced,  the  instrument  withdrawn  from 
the  vessel  containing  the  remainder  of  the  solution,  and  inverted, 
after  which  the  bell  e  is  removed  and  the  stopper  b  inserted  in  its 
place.  The  lysimeter,  now  closed  at  both  ends  by  the  stoppers,  is 
next  washed  exteriorly  with  a  little  alcohol,  and  laid  aside  to  cool. 
The  previously  ascertained  tare  of  the  stoppered  tube  deducted 
from  the  total  weight  of  tube  and  contents  leaves  the  net  weight 
of  the  solution  contained  in  it.  This  is  then  transferred  to  a  tared 
dish  or  beaker,  the  tube  is  carefully  rinsed  with  alcohol,  the  wash- 
ings being  added  to  the  solution,  which  is  then  evaporated  to  dry- 
ness  over  a  water-bath,  and  finally  the  residue  heated  to  dryness 
in  a  drying  oven  and  weighed.  . 

In  using  the  lysimeter  with  hot  solvents  the  instrument  should 
be  gradually  heated  to  the  temperature  required,  as  a  too  sudden 
change  might  cause  its  fracture. 

89.  Co-efficients  of  solubility.     The  number  of  weight  units  of 
any  substance  required  to  saturate  100  weight  units  of  water  at 
any  given  temperature  is  the  co-efficient  of  solubility  of  that  sub- 
stance at  that  temperature. 

We  have  stated  that  it  is  the  almost  universal  rule  to  give  the 
solubilities  of  solids  in  water  (and  in  alcohol)  at  the  temperature 
of  15°,  and  the  numbers  expressing  their  co-efficients  of  solubility, 
therefore,  refer  to  and  are  correct  at  that  temperature  only,  unless 
otherwise  expressly  stated.  Thus,  when  we  say  that  the  co-effi- 
cient of  solubility  of  borax  is  6.25  this  statement  means  that  100 
weight  of  units  of  water  at  15°  will  dissolve  6.25  weight  units  of 
borax  to  form  a  saturated  solution.  The  co-efficient  of  solubility 
of  sodium  arsenate  is  25  because  25  weight  units  of  the  salt 
Na2HAsO4.7H2O  will  form  a  saturated  solution  with  100  weight 
units  of  water  at  15°. 

This  method  of  expressing  ratios  of  solubility  has  the  advan- 
tage that  the  solubilities  of  different  substances  in  a  constant  quan- 
tity of  solvent  are  directly  represented  by  the  co-efficients  so  that 
comparisons  are  rendered  easy  and  direct.  Thus,  a  substance 
whose  co-efficient  of  solubility  is  10  is  twice  as  soluble  as  one 
whose  co-efficient  is  5,  in  the  same  quantity  of  solvent. 

90.  Another  and  more  common  method  of  stating  the  solubili- 
ties of  substances — a  method  employed  in  all  pharmacopoeias — is 
that  of  giving  the  number  of  weight  units  of  solvent  required  to 
dissolve  one  weight  unit  of  the  substance.     Thus  the  Pharmaco- 


SOLVENTS SOLUBILITY SOLUTIONS.  45 

poeia  tells  us  that  sodium  arsenate  is  soluble  in  4  parts  of  water  at 
15°,  and  that  borax  is  soluble  in  16  parts.  The  solubilities  of 
these  two  substances  are  in  inverse  ratio  as  the  numbers  express- 
ing the  respective  quantities  of  solvent  required  to  dissolve  them. 

91.  Both  methods  of  expression  are  useful,  and  in  laboratory 
operations  we  find  one  of  them  more  direct  and  convenient  in  one 
case,  and  the  other  preferable  in  another  case. 

In  this  book  we  shall  make  use  of  both  methods  according  to 
circumstances,  but  the  student  will  observe  that  the  co-efficients 
of  solubility  do  directly  express  the  proportions  in  which  sub- 
stances can  be  dissolved,  whereas  the  pharmacopoeial  method  does 
not  directly  express  the  solubility  of  the  substance  in  a  given  con- 
stant quantity  of  solvent,  but  the  proportion  of  solvent  required 
to  dissolve  a  constant  quantity  of  the  dissolved  substance. 

92.  The  student  will  see  that— 

The  number  of  weight  units  of  solvent  required  to  dissolve  I 
weight  unit  of  the  soluble  substance  is  the  reciprocal  of  the  num- 
ber of  weight  units  of  the  soluble  substance  required  to  saturate 
i  weight  unit  of  the  solvent,  and  vice  versa. 

And  as 

The  co-efficient  of  solubility  of  any  soluble  substance  is  the 
number  of  weight  units  thereof  required  to  saturate  100  weight 
units  of  the  solvent, 

Therefore, 

The  number  of  weight  units  of  solvent  required  to  dissolve  I 
weight  unit  of  the  soluble  substance  is  found  by  dividing  100  by 
its  co-efficient  of  solubility,  or,  in  other  words,  by  multiplying  the 
reciprocal  of  its  co-efficient  of  solubility  by  100. 

And— 

The  number  of  weight  units  of  any  soluble  substance  required 
to  saturate  i  weight  unit  of  the  solvent  is  found  by  dividing  the 
co-efficient  of  solubility  by  100. 

93.  Methods  of  fixing  and  expressing  the  strength  of  solutions. 
The  strength  or  degree  of  concentration  of  a  solution  may  be 
fixed  or  expressed  in  various  ways.     Probably  no  one  method  is 
equally  convenient  for  all  purposes ;  but  the  most  generally  useful 
and  accurate  method  is  to  express  the  strength  of  the  solution  in 
per  cent  by  weight. 

Among  the  various  methods  in  use  are  the  following: 

i.     The  employment  of  arbitrary  scales  of  degrees  of  density 


46  SOLVENTS SOLUBILITY SOLUTIONS, 

indicated  by  areometers  or  hydrometers,  such  as  the  scales  of 
Baume,  Twaddell,  and  others.  The  strength  of  salt  solutions, 
syrups,  acids,  gas  solutions,  etc.,  is  frequently  indicated  by  some 
special  hydrometer  scale. 

2.  The  actual  specific  weight  of  a  solution  may  be  employed  to 
indicate  its  relative  strength. 

3.  The  strength  of  a  solution  may  be  fixed,  as  is  often  done  in 
pharmaceutical  preparations,  according  to  the  number  of  custom- 
ary weight  units  of  the  soluble  substance  contained  in  any  con- 
venient volume  of  the  solution,  as,  for  instance,  the  number  of 
grains  or  ounces  to  each  fluidounce,  pint  or  gallon,  or  the  number 
of  grams  in  each  liter. 

4.  The  strength  of  mixtures  of  alcohol  and  water  is  some- 
times expressed  in  per  cent  by  weight,  sometimes  in  per  cent  by 
volume,  and  sometimes    in    arbitrary    degrees,    as    in    "degrees 
proof,"  etc. 

5.  The  strength  of  gas  solutions  may  be  expressed  in  per  cent 
by  weight,  or  according  to  the  number  of  volumes  of  the  gas  dis- 
solved by  each  volume  of  the  solvent,  and  in  other  ways.     It  is 
the  custom  to  state  the  strength  of  solution  of  hydrogen  dioxide 
according  to  the  number  of  volumes  of  "available  oxygen"  obtain- 
able from  each  volume  of  the  solution. 

6.  Volumetric  solutions   are  so  prepared  that   each   liter  of 
finished  solution  contains  as  many  grams  as  the  number  of  units 
expressing  the  molecular  weight  of  the  reagent,  divided  by  the 
number  expressing  the  valence  of  either  of  its  two  component 
radicals. 

7.  Solutions  may  also  be  made  for  laboratory  use  which  con- 
tain in  each  kilogram  as  many  grams  as  the  number  of  units  ex- 
pressing the  molecular  weight  of  the  dissolved  substance,  or  a 
convenient  decimal  proportion  thereof. 

8.  Finally,  the  strength  of  solutions  may  be  fixed  and  ex- 
pressed in  per  cent  by  weight,  as  is  the  custom  in  stating  the 
strength  of  acids  and  other  solutions  of  chemicals.    This  method 
is  the  most  convenient  and  scientific,  especially  if  at  the  same  time 
it  includes  the  principle  referred  to  in  the  preceding  paragraph,  so 
far  as  applicable  or  useful. 

The  molecular  weight  of  HC1  being  36.4,  it  would  be  more  con- 
venient for  laboratory  purposes  to  have  a  solution  (hydrochloric 
acid)  containing  36.4  per  cent  of  HC1  than  to  have  one  containing 
31.9  per  cent. 


CHAPTER  VI. 

THE  CLARIFICATION  OF  LIQUIDS.    STRAINERS.    PRESSES.    FILTRATION. 

94.  Unclear  liquids  are  mixtures  of  liquids  with  undissolved 
solid  matter,  or  mixtures  of  two  or  more  liquids  insoluble  in  each 
other. 

Liquids  containing  suspended  insoluble  solid  or  liquid  particles, 
or  mixed  with  any  insoluble  matter,  generally  require  clarification 
before  they  can  be  advantageously  employed. 

The  separation  of  the  undissolved  substances  is  effected  by 
some  one  of  the  various  methods  described  in  this  chapter. 

95.  Pieces  of  solids  floating  or  submerged  in  otherwise  clear 
liquids  may  be  removed  by  means  of  perforated  spoons  or  ladles, 
or  with  an  ordinary  spoon,  or  by  means  of  pincers.    If  the  solid 
is  heavier  than  the  liquid  the  latter  may  be  decanted  from  the 
solid,  or  it  may  be  removed  by  means  of  a  syphon. 

Perforated  porcelain  funnels,  such  as  Buchner's  funnel   (fig. 
18)  are  very  useful  for  the  separation    of 
solids  not  too  minutely  divided.     Perfor- 
ated discs  which  can  be  placed  in  ordinary 
funnels  are  also  much  used  (fig.  19). 

The  liquid  may  also  be  passed  through  a 
piece  of  coarse,  thoroughly  washed  sponge, 
or  a  loose  plug  of  pure  ("absorbent")  cot- 
ton, placed  in  an  ordinary  funnel  or  in  a 
cropped  funnel  (fig.  20). 

96.  Clarification  by  subsidence.     Solid 
matter  suspended  in  a  liquid  may  be  al- 
lowed  to  subside,  after   which   the  clear   Fig.  is.  Buchner  funnel  of 
liquid  is  decanted  or  drawn  off.     For  this 

purpose  the  turbid  liquid  should  be  put  in  a  tall  or  deep  vessel 
and  left  at  perfect  rest  until  all  of  the  solid  matter  has  settled  to 
the  bottom  in  as  compact  a  layer  of  sediment  as  its  character  may 
permit  it  to  form.  If  the  solid  matter  is  not  too  finely  divided  and 
if  its  density  is  greater  than  that  of  the  liquid  this  method  of  clari- 
fication is  readily  carried  out.  But  when  the  solid  particles  are 

47 


48 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


extremely  minute,  and  especially  when  their  density  is  about  the 
same  as  that  of  the  liquid,  the  operation  is  slow  and  difficult  if 
not  impossible.  It  is,  however,  frequently  practicable  to  suffi- 
ciently lower  the  density  of  the  liquid  by  dilution  or  by  raising  its 
temperature. 

Whenever  admissible  the  clarification  may  be  effected  by  adding 

a  rather  heavy  insoluble 
substance,  such  as  purified 
clay  in  powder,  which  car- 
ries the  other  solid  matter 
down  with  it  as  it  descends 
to  the  bottom  of  the  vessel. 
The  clay  or  other  sufficient- 
ly heavy  absorbent  powder 
employed  must  be  added  in 
moderate  quantity  and 


Fig.  19.  Perforated   disc   and   its   use   in   an  or- 
dinary funnel. 


Fig.  20.  Cropped  funnel. 


must  be  thoroughly  distributed  through  the  whole  body  of  the 
turbid  liquid  by  stirring. 

97.  Decantation.  A  clear  liquid  standing  over  a  solid  deposit 
of  crystals,  precipitate  or  sediment,  may  be  poured  off  free  from 
solid  matter.  A  complete  separation  of  the  liquid  by  this  method 
is  rarely  possible,  but  it  may  frequently  be  carried  far  enough  to 
prove  a  valuable  labor-saving  process. 

To  pour  a  liquid  from  one  vessel  into  another  without  spilling 
is  sometimes  a  difficult  feat,  but  it  is  one  which  every  laborant 
must  practice  until  mastered. 

The  practical  precautions  to  be  observed  in  this  connection  are : 
I,  never  to  quite  fill  any  vessel  with  liquid,  but  to  leave  enough 
room  to  admit  of  tilting  the  vessel  considerably  before  any  of  the 


CLARIFICATION    OF    LIQUIDS — STRAINERS,    ETC.  49 

liquid  can  run  over  the  edge  or  lip ;  2,  to  use  vessels  of  suitable 
shape,  with  a  flaring  top  or  rim  or  provided  with  a  lip ;  and  3,  to 
handle  the  vessel  with  care,  deliberately  (yet  deftly)  and  with  a 


Fig.  21.  Decantation  over  a  greased  rim. 


Fig.  22.  Decantation  by  means  of  the   "guiding  rod." 

steady  hand.  The  rim  or  edge  over  which  the  liquid  is  to  pass 
may  be  greased  to  obviate  capillary  attraction  and  thus  prevent 
the  liquid  from  running  down  along  the  outside  of  the  vessel. 


Vol.    II— 4 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


Fig.  23.  Porcelain  casserole. 


Another  plan  is  to  use  a  "guiding  rod"  to  give  the  stream  of  liquid 
the  proper  direction. 

98.  The  transfer  of  liquids  from  one  vessel  to  another  is  also 
effected  in  various  other  ways,  as  by  means  of  casseroles,  pitchers, 
pipettes,  syphons,  etc. 

Casseroles  are  dippers  with  lips  and  handles  (fig.  23).  They 
are  generally  made  of  porcelain,  and 
are  used  principally  for  transferring 
considerable  quantities  of  liquids,  in 
portions,  from  one  vessel  to  another 
in  the  course  of  laboratory  processes 
for  the  production  of  chemicals. 

Pipettes  (fig.  24)  are  used  for  transferring  small  quantities  of 
liquids.  They  are  usually  of  glass  and  graduated. 

99.  Syphons  and  their  use.  Syphons  of  glass  and  of  rubber  tub- 
ing are  indispensable,  and  are  used  for  transferring  liquids  from 
vessels  which  can  not  or  should  not  be  moved  or 
disturbed.     Clear    liquids    may    be    almost    com- 
pletely  withdrawn    from    heavy    precipitates    and 
sediments  by  means  of  the  syphon. 

Syphons  of  glass,  porcelain  or  earthenware  are 
also  employed  for  transferring  solutions  of  acids 
or  alkalies  and  other  corrosive  liquids  from  large 
containers,  and  for  controlling  the  gradual  addi- 
tion of  one  liquid  to  another  in  processes  of  pre- 
cipitation, oxidation,  etc. 

A  variety  of  glass  syphons  will  be  found  useful 
in  any  large  pharmaceutical  laboratory.  Their 
construction  and  operation  are  shown  in  figs.  25 

£O   2j  Fig-  24-  Pipettes. 

Flexible  pure  rubber  tubing  of  from  10  to  20  millimeters  diam- 
eter is  extremely  convenient  for  syphoning.  It  may  be  required 
in  lengths  varying  from  600  millimeters  to  2  meters. 

Two  straight  pieces  of  glass  tubing  connected  by  a  rubber  tub- 
ing joint  make  a  good  syphon. 

Syphons  work  on  the  principle  that  "liquids  seek  their  own 
level"  through  the  force  of  gravitation.  The  syphon  is  a  tube  bent 
so  that  its  two  limbs  would,  if  straight,  meet  at  an  acute  angle. 
When  about  to  be  used,  the  instrument  is  filled  with  the  liquid 
which  is  to  flow  through  it ;  one  limb  is  then  inserted  in  the  vessel 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


from  which  the  liquid  is  to  be  withdrawn,  and  the  other  limb  in 
the  receiving  vessel.  The  greater  weight  of  the  liquid  in  the 
longer  limb  of  the  syphon  will  cause  it  (the  liquid)  to  flow  down- 


Fig.  25.  Simple  syphon. 

ward,  and  the  atmospheric  pressure  causes  the  ascent  of  fresh 

liquid  through  the  shorter  limb  so  that  the  flow  is  uninterrupted 

until  the  level  of  the  liquid 

in  both  vessels  is  the  same. 

When  the   level   of  the   two 

bodies  of  liquid  connected  by 

the  syphon  is  the  same  it  is 

evident    that    the    weight    of 

the  column  of  liquid  in  one 

limb    is    the    same    as    the 

weight   of   the   liquid   in   the 

other     limb,     equilibrium     is 

established,       and       the       flow   Fig.  26.  Glass  syphons  for  acids  and  other 

ceases;   if    now    one    of    the  corrosive  liquids. 

two  vessels  be  lowered  the  flow  of  liquid  through  the  syphon  will 

begin  again  in  the  direction  of  the  lower  vessel. 

100.  Colation.  Filtration  through  comparatively  coarse  media 
is  called  eolation,  and  the  liquid  partially  freed  from  solid  particles 
by  eolation  or  straining  is  called  the  colature.  Mixtures  of  liquid 
and  solid  matter  are  strained  through  sieves  and  through  various 
kinds  of  strainers. 

Unbleached  muslin  is  the  most  generally  useful  straining  cloth 
for  ordinary  laboratory  operations  in  the  production  of  inorganic 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


chemicals.  The  cotton  cloth  should  be  boiled  in  water  before  it  is 
used  in  order  to  remove  starch  or  other  "sizing"  and  "filling" 
material.  It  should  be  cut  into  square  pieces  of  various  sizes  to 
suit,  and  always  larger  than  the  frame  upon  which  it  is  to  be  fas- 
tened for  use.  The  most  useful  size  of  cloth  strainer  for  the 
manufacturing  laboratory  is  perhaps  600  millimeters  square,  and 
the  stand  required  to  hold  such  a  strainer  should  be  about  450 

millimeters  square  and 
about  400  millimeters 
high,  so  that  a  stone 
jar  of  about  15  liters 
capacity  may  be  placed 
under  it.  The  strainer 
must  be  larger  than  the 
frame  in  order  that  a 
sufficient  margin  may 
be  left  for  fastening  the 
cloth  on  the  wooden 
frame  and  for  the  neces- 
sary "bagging"  of  the 
strainer  in  addition  to 
the  allowance  which 
must  be  made  for 
shrinking. 

The     straining     cloth 
frame  should  be  strong 
enough    to    stand    con- 
stant use,   and  must  be 
provided     with     strong 
pointed   nails   above   on 
which    to    fasten    the 
strainer.     Square  frames 
four  legs   are   much 
than    circular    or 
triangular  frames   on   three   legs.    In   addition  to   the   strainer 
stands,  or  frames  on  legs,  an  assortment  of  square  frames  with- 
'out  legs  is  also  useful.     Such  a  strainer  frame  is  called  a  "ten- 
aculum."     (Fig.  29.) 

Whenever  the  strainer  is  to  be  used  for  straining  an  aqueous 
fluid  it  should  first  be  wetted  in  order  to  diminish  the  diameter  of 


iiiiiiiMiiiii 


Fig.  27.  Arrangement   for  continuous   filtration   by   oil 
means   of   syphons. 

better 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


53 


the  openings  in  the  cloth  by  the  swelling  of  the  threads  of  which 
it  is  woven,  and  to  establish  uniform  capillary  attraction. 

When  large  quantities  of  very  heavy  precipitates  are  to  be 
washed  or  collected  on  a  cloth  strainer,  care  should  be  taken  to 
make  the  strainer  strong  enough  to  bear  the  weight  of  the  precip- 
itate and  the  water.  If  a 
single  thickness  of  the  mus- 
lin is  not  strong  enough,  it 
is  necessary  to  double  it  or 
to  support  the  sag  by  broad 
muslin  bands  crossing  each 
other  under  it,  unless  strong- 
er muslin  is  at  hand  which 
is  open  enough  to  be  suitable. 


Fig.  28.  Muslin  strainer  on  stand. 


Fig.  29.  Tenaculum. 


Closely  woven  cotton  cloth  is  not  as  suitable  as  a  looser  fabric. 
Linen  is  rarely  used  for  strainers,  but  flannel  is  sometimes  more 


Fig.  30  and  31.  Method  of  folding  and  twisting  a  small  strainer. 

effective  than  muslin,  and  seamless  felt-bags  are  occasionally  still 
more  effective,  as  in  the  filtration  of  syrups  and  of  liquids  con- 


54  CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 

taining  undissolved  particles  of  volatile  oil  or  other  liquid  sub- 
stances in  suspension. 

Pointed  straining  bags  are  also  made  of  muslin  and  of  flannel, 
and  of  "Canton  flannel,"  as  well  as  of  felt. 

The  manner  in  which  a  strainer  is  folded  and  twisted  to  squeeze 
the  liquid  through,  after  it  has  ceased  to  run  of  its  own  weight,  is 
shown  in  figs.  30  and  31.  When  the  quantity  of  wet  mass  in  the 
strainer  is  small  in  proportion  to  the  size  of  the  cloth,  and  the  cloth 
not  too  large,  it  may  be  sufficient  to  twist  the  folded  strainer  with 
the  hands.  But  when  larger  quantities  are  operated  upon  a  press 
is  necessary  (par.  101). 

In  most  cases,  however,  it  is  most  advantageous  to  allow  the 
wet  mass  to  remain  on  the  strainer  until  completely  drained  and 
sufficiently  free  from  moisture  to  be  spread  out  to  dry,  if  the 
solid  matter  be  the  product  and  the  liquid  valueless. 

Quantities  of  liquid  exceeding  two  liters  are  usually  filtered  on 
strainers,  lined  with  paper  pulp  if  necessary,  while  smaller  quan- 
tities should  be  filtered  on  funnels. 

Liquids  filtered  through  cloth  strainers,  and  even  through  paper 
filters,  do  not  always  pass  through  quite  clear  from  the  start ;  they 
should  then  be  returned  to  the  filter  until  the  filtrate  runs  clear. 

To  hasten  the  process  the  filter  or  strainer  may  constantly  be 
kept  nearly  full  until  all  of  the  liquid  to  be  filtered  has  been  added. 
But  the  filtration  can  not  be  hastened  by  scraping  the  sides  of 
the  filter  or  strainer  if  a  clear  filtrate  is  desired.  Whenever  prac- 
ticable (as  in  a  large  laboratory)  the  straining  stands  used  for 
washing  precipitates  should  stand  on  an  asphalt  floor  inclined  to- 
ward one  or  more  gutters  connected  with  the  drain  pipes  through 
which  the  valueless  washings  may  pass  away. 

101.  Presses.  To  express  the  liquid  from  voluminous  mag- 
mas or  wet  precipitates  holding  large  quantities  of  water  a  strong 
screw  press  is  necessary.  A  practical,  serviceable  press  must  not 
be  too  small,  because  satisfactory  results  can  not  be  obtained  when 
the  quantities  operated  upon  are  so  great  as  to  tax  the  capacity  of 
the  press  to  hold  them.  This  is  especially  true  of  presses  con- 
structed like  the  ordinary  pharmaceutical  tincture  press  in  which 
the  solid  matter  subjected  to  the  pressure  is  confined  in  a  cylinder. 

The  mass  of  wet  solid  matter  must  be  placed  in  the  center  of  a 
strong  press  cloth,  which  is  then  folded  so  as  to  securely  enclose 
the  mass,  and  the  size  of  the  package  must  not  be  so  large  as  to 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC.  55 

cover  the  whole  botton  of  the  press  within  the  cylinder,  but  should 
be  of  smaller  diameter  than  that  of  the  press  block,  so  that  plenty 
of  room  will  be  left  around  the  bundle  for  the  escape  of  the 
liquid  expressed  from  it.  Most  of  the  failures  in  operating  simple 
presses  are  due  to  the  choking  occasioned  by  trying  to  work  on 
larger  quantities  of  material  than  can  be  advantageously  handled 
at  one  time.  Small  presses  of  brittle  cast  iron  with  press  blocks 
of  the  same  material  and  cylinders  of  tinned  or  galvanized  sheet 
iron  are,  therefore,  useless.  Presses  should  instead  be  made  of 
cast  steel,  or  of  hard  wood,  or  of  strong  porcelain. 

The  pressure  should  be  applied  slowly  or  gradually.    After  a 


Fig.  32.  Witt's   press,   with   press   block   of  strong 
porcelain. 

twist  or  two  of  the  screw  the  liquid  should  be  permitted  to  run 
until  it  stops  before  the  screw  is  turned  again.  The  final  pressure 
should  be  strong. 

When  no  more  liquid  can  be  squeezed  out  of  the  solid  material 
in  the  press  cloth  the  screw  should  be  turned  back ;  the  package 
should  be  removed  and  the  cloth  unfolded,  after  which  the  con- 
tents may,  if  necessary,  be  broken  up  and  mixed  and  again  en- 
folded in  the  cloth,  replaced  in  the  press  and  subjected  to  ex- 
pression a  second  time.  A  second  treatment  in  the  press  is, 
however,  rarely  necessary  in  working  upon  inorganic  substances. 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


Several  serviceable  presses  are  pictured  here,  two  with  one 
screw  and 'one  with  two.  One  of  the  best  is  Witt's  press.  Hy- 
drostatic presses  and  filter  presses  required  for  operating  upon 
very  large  quantities  of  material  will  be  found  described  in  larger 
works  on  chemical  technology  and  in  the  illustrated  price  cata- 
logues of  the  makers  of  such  apparatus. 

Cylinder  presses  of  from  five  to  ten  liters  capacity  are  probably 

the  most  useful  in  pharmaceuti- 
cal laboratories. 

102.  Corrosive  liquids  may  be 
filtered  through  various  filtering 
media  not  affected  by  them. 
Acids,  alkali  solutions,  solu- 
tions of  zinc  chloride  and  other 
corrosive  solutions,  when  un- 
clear, may  generally  be  success- 
fully clarified  by  subsidence  and 
decantation  or  by  drawing  off 
the  clear  portion  by  means  of 
glass  syphons.  But  they  may 
be  filtered,  when  necessary, 

Fig.  33.  Cylinder  press. 

through  washed  sand, 
coarsely  powdered 
glass  or  porcelain, 
glass  wool,  asbestos, 
powdered  pumice 
stone,  or  powdered 
clay,  according  to  cir- 
cumstances. 

103.  Paper  filters. 
Filtration  through 
paper  is  an  extremely 
important  and  valu- 
able method  of  clari- 
fying liquids,  and  it  is 
applicable  to  nearly  Fig-  34t  Mohr's  double  screw  press- 

all  liquids  which  are  not  corrosive,  or  too  viscous.  Filter  paper 
is  unsized,  porous  paper,  made  expressly  for  the  special  use  its 
name  implies. 

Gray  filter  paper  is  made  of  inferior  material  and  should  never 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC.  57 

be  used  for  pharmaceutical  or  chemical  purposes  because  it  may 
not  only  contain  iron  and  other  objectionable  inorganic  impuri- 
ties, but  is  more  liable  to  be  infected  with  bacteria  than  white 
paper. 

White  filter  paper  is  made  of  several  grades  of  purity,  thick- 
ness and  porosity.  A  chemically  pure  filter  paper  leaving  scarcely 
any  ash  on  ignition  is  required  for  some  purposes  in  quantitative 
chemical  analysis;  but  for  other  chemical  and  pharmaceutical 
work  it  is  only  necessary  that  the  white  filter  paper  shall  be  free 
from  iron  and  other  impurities  soluble  in  or  affecting  the  purity 
of  the  liquids  which  may  be  filtered  through  it.  The  paper 
should  be  so  pure  and  clean  that  even  hot  solutions  of  salts  (ex- 
cept such  salts  as  may  chemically  attack  the  cellulose  of  which 
the  paper  consists)  may  be  filtered  through  it  without  the  slight- 
est discoloration  and  without  taking  up  even  traces  of  any  sub- 
stance from  it. 

Filter  paper  of  very  close  texture  (less  porous  paper)  is  re- 
quired for  the  removal  of  extremely  fine  particles  of  solid  matter ; 
filter  paper  of  loose  texture,  or  more  porous  paper,  is  sufficient  for 
the  removal  of  coarser  particles,  and  is  necessary  for  rapid  filtra- 
tion. 

Lighter  paper  is  suitable  for  thin  and  light  liquids,  such  as 
alcohol,  etc. ;  heavier  and  coarser  paper  is  preferred  for  the  rapid 
filtration  of  water-solutions  of  inorganic  substances,  especially 
if  the  solutions  be  heavy ;  still  coarser  or  more  porous  paper  is 
necessary  for  the  filtration  of  thick  liquids  such  as  syrups,  oils, 
etc. 

"Hardened  paper  filters"  are  best  for  the  collection  and  washing 
of  precipitates  and  for  "pressure  filtration." 

Filter  paper  is  sold  in  rectangular  sheets  as  well  as  in  cir- 
cular form.  Circular  filters  are  made  to  fit  the  ordinary  sizes  of 
filter  funnels.  Whole  sheets  of  filter  paper  may  be  used  for  cut- 
ting round  filter  paper;  but -this  is,  of  course,  a  wasteful  practice. 
Sheets  of  bibulous  white  filter  paper  are  used  mostly  for  absorb- 
ing water  from  precipitates,  masses  of  small  crystals,  and  other 
wet  products. 

104.  When  paper  filters  are  used  for  collecting  and  washing 
precipitates,  they  should  be  plain  filters  which  fit  the  funnel  snugly 
so  as  fo  come  in  contact  with  and  be  supported  by  the  inner  sides 
of  the  funnel  at  all  points  in  order  that  the  precipitate  may  not 


CLARIFICATION     OF    LIQUIDS STRAINERS,    ETC. 


be  spread  upon  a  larger  area  of  the  paper  than  necessary,  for  if 
finely  divided  precipitates  come  in  contact  with  a  greater  surface 
some  loss  must  be  occasioned  thereby. 

Plain  filters  are  also  used  in  perforated  funnels,  in  ribbed  fun- 
nels, and  in  filter  baskets;  all  of  which  facilitate  the  passage  of  the 
liquid  through  the  paper  by  providing  openings  and  channels 
through  which  it  may  readily  escape. 

As  a  "plain  filter"  when  opened  forms  a  cone,  the  apex  of 
which  has  an  angle  of  60  degrees,  it  fol- 
lows that  the  funnel  used  for  such  a  filter 
must  be  of  the  same  angle. 

But  when  a  plain  filter  is  used  in  a 
plain  funnel  of  60  degrees  angle,  the 
liquid  can  pass  through  the  paper  only 
at  the  apex  of  the  filter  in  the  throat  of  the 
funnel  where  the  paper  is  not  in  contact 
with  it.  This  would  make  the  escape 
of  the  liquid  very  slow,  which  is  a  decided 
disadvantage  except  in  the  washing  of 
precipitates.  Moreover,  the  whole  weight 
of  the  superincumbent  liquid  resting  upon 
the  paper  at  the  apex  of  the  filter,  when  the  liquid  is  a  heavy 
one  and  the  filter  full,  may  cause  the  paper  to  break  at  that 
point.  To  prevent  this  trouble,  which  is  sometimes  serious,  the 
paper  filter  may  be  supported  at  its  apex  by  an  additional  cone  or 
filter  of  paper  (or  of  perforated  platinum)  or  of  muslin.  A  paper 
filter  "shod"  with  a  muslin  tip  placed  in  the  throat  of  the  funnel 
is  to  be  preferred  to  a  "double  filter"  or  a  paper-shod  filter. 


Fig.  35.  Corrugated   funnel 
for  rapid  filtration. 


Fig.  36.  Perforated 
porcelain  funnel 
for  filtration. 


Fig.  37.  Perforated 
porcelain  fun- 
nel for  draining 
crystals  or  for 
filtration. 


Fig.  38.  Perforated 
platinum  cone 
for  filtration  by 
pressure. 


Plaited  filters  are  the  most  useful  paper  filters  for  rapid  filtration 
when  plain  funnels  are  used  without  filter  baskets. 

105.  How  to  fold  paper  filters.  A  circular  piece  of  filter  paper 
may  be  folded  into  a  plain  paper  filter  by  making  the  first  fold 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


59 


a  straight  line  through  the  center,  the  crease  thus  made  being 
coincident  with  the  diameter  of  the  circle ;  the  second  fold  is 
then  made  through  the  center  of  the  first  fold  and  at  right  angles 
with  it;  a  third  fold  is  next  made,  again  dividing  the  folded 

paper  into  two  equal  segments 
of  the  circle,  the  crease  running 
from  the  apex  to  the  edge.  The 
folded  paper  is  now  opened  up 
until  the  half-circle  is  reached, 
after  which  the  flaps  are  laid 
back  on  opposite  sides  against  the 
second  fold,  and  the  two  center 
edges  of  the  filter  are  then  parted 
so  that  the  cone  thus  formed  pre- 
sents three  thicknesses  of  paper 
on  two  opposite  sides  with  a  single 
thickness  of  paper  on  the  two 
other  opposites,  as  shown  in  Fig. 

39- 

A  plain  filter  may  be  made  out 
of  one  half-circle  of  filter  paper, 
as  shown  in  Fig.  40,  and  this 
kind  of  paper  filter  may  be  made 
to  fit  any  funnel,  since  the  fold  can  easily  be  made  broader 
either  at  the  base  or  at  the  apex  of  the  cone  so  as  to  give  any  angle 
desired.  This  filter,  as  will  be  seen,  requires  the  use  of  only  half 


Fig.  39.  Plain  paper-filter. 


Fig.  40.  Simple   filter  made  of 
one  half-circle  of  ppper. 


Fig.  41.  Plaited  paper  filter. 


as  much  paper,  which  makes  it  the  most  economical  paper  filter 
that  can  be  made. 

The  plaited  filter  can  be  made  in  various  ways.  The  most  com- 
mon method  is  sufficiently  illustrated  by  fig.  41. 

Plaited  filters  may  be  used  with  funnels  of  any  angle. 


6o 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


106.  Double,  treble  and  even  quadruple  paper  filters  and  cloth 
strainers  are  sometimes  used  when  a  single  thickness  of  the  paper 
or  cloth  is  insufficient  to  produce  a  clear  filtrate.    But  some  tur- 
bid liquids  holding  extremely  finely  divided  solid  matter  in  sus- 
pension, or  containing  some  insoluble  liquid  distributed  through 
it  with  which  it  forms  an  emulsion,  can  not  be  rendered  clear 
by  any  process  of  filtration.     The  pores  of  the  paper  may  be 
gradually  entirely  closed  by  finely  divided  precipitates,  very  vis- 
cous fluids  (like  strong  mucilages,  strong  solutions  of  albumin, 
etc.)  do  not  pass  through  filter  paper  at  all,  and  "emulsions"  of 
mixed  liquids  pass  through  without  separation  if  at  all. 

107.  Hot  filtration.     Many 
liquids    which,    when    cold, 
refuse    to    pass    through    the 
ordinary   filtering   media,   in- 
cluding  paper,   may  be   suc- 
cessfully   filtered    when    hot. 
Again,    many    liquids    which 
pass  through  the  filter  slowly 


Fig.  42.  Funnel  in  hot-water- 
jacket  for  hot  filtration. 


Fig.  43.  Arrangement  for  hot  filtration. 


when  cold,  may  pass  less  slowly  or  even  rapidly  when  hot. 

Jacketed  funnels  (Figs.  42  to  44)  are  employed  for  hot  filtra- 
tion, and  also  conical  coils  (Fig.  45). 

108.  Rapid  filtration  is,  in  special  cases,  effected  by  hydrostatic 
pressure  or  by  suction. 

One  good  contrivance  is  a  box  having  perforated  sides  and  cov- 
ered on  the  outside  with  the  straining  cloth  (or  filter  paper  next  to 
the  box  and  cloth  over  it)  securely  fastened,  this  box  to  be  pro- 
vided with  "a  tube  through  which  a  syphon  can  be  inserted  by 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


61 


means  of  which  the  filtrate  accumulating  in  the  box  can  be  drawn 
off.  This  box  is  then  submerged  in  the  turbid  liquid  to  be 
filtered,  when  the  hydrostatic  pressure  causes  the  liquid  to  pass 
through  the  cloth  (and  paper)  into  the  box. 


Fig.  44.  Dietrich's  jacketed  funnel 
for  hot  filtration;  used  with 
steam  heat. 


Fig.  45.  Hot-water-coil   for   hot 
filtration. 


Various   kinds   of   ''filter   pumps"   are   also   used  to  create  a 
partial  vacuum  in  the   receiving  vessel   into  which  the  filtrate 


Fig.  46.  Filtration   under   pressure   by   means   of   a   filter 
pump  which  exhausts  the  air  from  the  flask. 

passes  so  as  to  cause  suction  through  the  filter.     One  such  filter 
pump  is  shown  in  Fig.  46. 


62 


CLARIFICATION    OF    LIQUIDS STRAINERS,    ETC. 


A  perforated  filtering  disc  of  porcelain  with  a  rubber  tire 
around  its  grooved  edge,  is  placed  in  the  funnel  and  cov- 
ered with  filter  paper,  muslin,  or  both,  or  flannel,  as  may  be  re- 
quired. The  funnel  is  fitted  tightly  into  the  neck  of  a  strong  re- 
ceiving bottle  (Fig.  47)  and  this  is  connected  by  a  side-tube  with 
the  filter  pump.  (See  also  Fig.  19.) 


Fig.  47.  Use   of   perforated    discs    Fig.  48.    Arrangement 
for    filtration  under  pressure.  for    continuous    fil- 

tration. 


Fig.  49.  Illustrates  an 
arrangement  for  the 
automatic  flow  of 
liquid  in  filtration. 


109.  Continuous  filtration.  Figures  48  and  49  illustrate  a  sim- 
ple arrangement  for  a  continuous  flow  of  liquid  into  the  funnel 
for  filtration  or  for  washing  precipitates. 

Continuous  filtration  may  also  be  effected  by  a  syphon  arrange- 
ment as  shown  in  Fig.  27. 


CHAPTER  VII. 

EVAPORATION. 

110.  The  temperature  at  which  any  substar^eYassumes  the 
state  of  vapor  depends  upon  its  constitution  and  urVm  the  pres- 
sure to  which  it  may  be  subjected.  Different  subs.taJices  exhibit 
greater  or  less  differences  as  to  their  vapor  liability  .according 
to  their  composition.  N 

Many  substances  remain  solid  at  the  highest  temperatures  pro- 
ducible ;  others  may  be  liquefied  but  not  valorized ;  others  decom- 
pose before  they  undergo  any  change  of  their  state  of  cohesion  or 
aggregation ;  many  kinds  of  compjpun^rnVtter  exist  only  in  the 
.  gaseous  state  under  ordinary  conditions  of  temperature  and  pres- 
sure; but  numerous  compounds\whicn  ark/solid  or  liquid  under 
ordinary  conditions  can  be  morkj^r  less  readily  converted  into 
vapor  by  sufficient  heat,  o/Vv  reducing  the  pressure  to  which  they 
are  exposed,  or  by  both  of  the^fe  means. 

The  power  with  whichVgases  and  vapors  resist  compression 
into  the  liquid  or  solid  state  is  called  their  vapor  tension. 

But  the  conversion  of  solids  and  liquids  into  vapors  depends 
not  upon  composition,  temperature  and  pressure,  only;  it  may 
be  greatly  affected  bypvarious  forms  of  molecular  attraction. 
Heat  opposes  molecujAr  attraction  and  therefore  breaks  down 
cohesion  ;  pressure,  pn  the  contrary,  aids  cohesion.  But  the  molec- 
ular attraction  between  different  kinds  of  matter  may  oppose  and 
in  mafty  caseSTwercome  the  cohesion  between  like  molecules. 


Thus  wat 

if  the  air 

air  for  w 

111. 

temperature 


r  passes  off  from  ice  even  at  the  freezing  point 
Hiding  the  ice  is  dry — i.  e.,  if  the  avidity  of  the 
not  already  satisfied. 

point.     The  boiling  point  of  any  liquid  is  the 
ond  which  it  can  not  continue  in  the  liquid  state 
v   of  cohfcfcib'h  witrrout  the  aid  of  increased  pressure. 
\    /TheMDoiling  point  of  any  given  liquid  is  constant  under  con- 
n)t  pressure. 

rbon  dioxide  boils  at  — 42°. 44  C. ;  ether  at  37° ;  alcohol  at 
78°  ;  water  at  100°  ;  mercury  at  357°  ;  and  zinc  at  940°.     These 

63 


64  EVAPORATION. 

boiling  points  refer  to  the  ordinary  atmospheric  pressure;  they 
rise  as  the  pressure  is  increased  and  fall  with  diminished  pres- 
sure. 

The  boiling  point  of  any  liquid  is,  in  other  words,  the  tempera- 
ture at  which  the  tension  of  its  vapor  is  greater  than  the  pres- 
sure which  it  sustains. 

112.  Evaporation  is  the  formation  of  vapor  at  or  from  the  sur- 
face of  any  solid  or  liquid  at  any  temperature  below  its  boiling 
point. 

When  comparatively  rapid  evaporation  is  desired  it  is  aided  by 
the  application  of  heat,  by  the  diminution  of  pressure,  and  by 
other  means. 

When  very  slow  evaporation  is  desired,  as  is  frequently  the 
case  in  the  production  of  crystallized  salts,  no  heat  is  applied. 
Evaporation  without  the  application  of  heat  is  called  spontaneous 
evaporation. 

Evaporation  depends  largely  upon  molecular  attraction  between 
the  molecules  of  the  vapor  and  the  molecules  of  the  components 
of  the  superimposed  air.  This  attraction  is  closely  akin  to  that 
which  causes  solution. 

113.  Vaporization,  as  this  term  is  generally  used,  means  the 
formation  of  vapor  at  the  boiling  point,  and  it  differs  from  evapo- 
ration chiefly  in  the  fact  that  the  vapor  which  is  formed  at  the 
boiling  point  of  any  liquid  is  not  formed  at  or  from  the  surface  of 
the  liquid,  but  in  the  body  of  it,  and  mainly  at  the  surface  of 
contact  between  the  liquid  and  that  portion  of  the  vessel  contain- 
ing it,  which  is  directly  exposed  to  the  source  of  heat 

114.  The  rate  of  evaporation  or  vaporization  of  any  liquid  de- 
pends upon  various  conditions,  among  which  the  following  are  the 
most  important : 

1.  The  volatility  of  the  liquid,  which  depends  upon  its  con- 
stitution or  composition.     Thin,  mobile,  less  cohesive  liquids  are 
more  volatile,  even  if  of  greater  specific  weight,  than  thick,  co- 
hesive liquids ;  but  the  specific  resistance  of  any  liquid  to  its  con- 
version into  vapor,  or,  in  other  words,  the  relative  force  of  attrac- 
tion between  its  molecules,  must  depend  primarily  upon  its  chemi- 
cal structure. 

2.  The  temperature  which  the  liquid  attains  has  a  direct  and 
decided  influence  upon  the  rate  of  evaporation.    A  boiling  liquid 


EVAPORATION.  65 

remains   of   constant   temperature,   but   the   rate   of   evaporation 
below  the  boiling  point  is  greater  the  higher  the  temperature. 

3.  The  supply  of  heat  for  the  formation  of  the  vapor  has  an 
important  bearing,  because  the  quantity  of  heat  motion  neces- 
sary  for  that  purpose   is   a  fixed   quantity  for  each   substance.- 
Whenever  any  given  liquid  passes  into  vapor  it  takes  up  a  definite 
quantity  of  heat  which  is,  therefore,  called  the  latent  heat  of  its 
vapor.     The  latent  heat  of  any  given  kind  of  vapor  is  a  constant 
quantity ;  it  does  the  work  of  keeping  the  substance  in  the  state, 
of  vapor,  is  the  cause  of  its  vapor  tension,  and  is  liberated  when- 
ever the  vapor  is  condensed. 

The  rapid  or  free  application  of  high  heat  must,  therefore,, 
favor  a  rapid  rate  of  vaporization. 

In  this  connection  we  must  consider  the  thermal  conductivity 
of  the  vessel  in  which  the  liquid  is  heated,  and  also  the  extent 
of  surface  of  that  vessel  with  which  the  flame  or  other  source  or 
means  of  application  of  the  heat  comes  in  direct  contact. 

Shallow  vessels  are  more  effective  than  deep  ones  if  only  the 
bottom  of  the  vessel  is  exposed  to  the  heat  applied.  Silver  dishes 
are  more  effective  than  any  other  because  silver  is  the  best  con- 
ductor of  heat  known. 

4.  The  pressure  to  which  the  liquid  is  subjected  reduces  the 
rate  of  evaporation  by  resistance  to  the  vapor  tension.     Heavy 
liquids,  other  conditions  being  equal,  do  not  evaporate  as  rapidly 
as  lighter  liquids. 

Solutions  and  mixtures  which  acquire  increased  density  by  the 
concentration  due  to  the  evaporation  of  the  solvent,  or  of  one  of 
its  more  volatile  constituents,  do  not  have  constant  boiling  points, 
except  saturated  solutions.  When  a  dilute  aqueous  salt  solution 
is  boiled  its  boiling  point  rises  as  the  solution  becomes  more  and 
more  concentrated  and  does  not  become  stationary  until  a  satur- 
ated solution  is  formed.  The  higher  boiling  point  is  here  caused 
by  increased  pressure. 

Deep  vessels  are  unfavorable  to  rapid  vaporization  if  filled  or 
nearly  so  for  the  vapor  is  formed  mainly  at  the  bottom,  and  if 
the  depth  of  the  liquid  is  great  the  vapor  must  be  formed  under 
greater  pressure.  The  release  of  the  vapor  may,  however,  be  fa- 
cilitated by  stirring. 

5.  The  rate  of  evaporation  or  vaporization  is,  finally,  aided  by 
molecular  attraction  between  the  -capoi\  formed  and  the  gases. 

Vol.    II— 5 


66  EVAPORATION. 

of  which  the  air  consists.  The  proportional  extent  of  surface  of 
the  evaporating  or  boiling  liquid  which  comes  in  contact  with 
the  air  is,  therefore,  a  matter  of  importance,  not  only  because 
greater  depth  causes  increased  pressure  upon  the  lower  strata  of 
the  liquid,  but  also  because  actual  contact  is  necessary  to  the 
diffusion  of  the  vapors  into  the  air.  This  is  an  additional  reason 
for  preferring  shallow  vessels  rather  than  deeper  ones. 

The  surface  of  contact  between  the  air  and  the  liquid  may  be 
increased  by  stirring  the  latter. 

The  humidity  of  the  air  in  contact  with  the  liquid  also  has  its 
effect  upon  the  rate  of  evaporation  of  water,  for  the  power  of  the 
air  to  absorb  the  vapor  is  not  unlimited. 

The  rate  of  evaporation  or  vaporization  is  greatest  when  the 
air  is  free  from  vapor  of  the  same  kind  as  that  being  formed,  and 
when  the  air  into  which  the  vapor  passes  becomes  saturated  with 
it,  no  further  aid  is  to  be  derived  from  the  contact  of  the  liquid 
with  that  air.  Currents  of  warm,  dry  air  over  the  surface  of  the 
liquid  greatly  hasten  the  formation  of  vapor,  and  such  currents 
are  created  by  stirring  the  liquid  as  well  as  by  other  simple 
means,  whereby  the  saturated  air  is  removed  and  replaced  by  a 
fresh  supply  capable  of  taking  up  the  vapor. 

115.  The     objects     of    evaporation    and    vaporization    are: 
i,  to  concentrate  solutions  by  the  elimination  of  a  part  of  the 
solvent ;  2,  to  obtain  saturated  solutions  for  the  purpose  of  caus- 
ing crystallization ;  3,  the  completely  separate  volatile  liquids  from 
solutions  and  mixtures. 

Liquids  are  evaporated:  i,  to  dryness;  2,  to  a  given  volume; 
3,  to  a  given  weight ;  4,  to  a  given  density ;  5,  to  a  certain  more  or 
less  definite  consistence;  6,  to  the  point  at  which  solid  matter 
begins  to  separate;  7,  to  a  constant  weight  (i.  e.,  until  there  is 
no  further  loss  of  weight);  or  8,  until  a  certain  objectionable  vola- 
tile constituent  or  impurity  shall  have  been  completely  expelled. 

116.  Boiling- vessels  should  be  deep  if  rapid  vaporization  is  to 
be  avoided  as  far  as  practicable — i.  e.,  when  the  object  is  the 
maintenance  of  the  boiling  point  purely  for  its  chemical  effects. 
Deep  dishes,  dishes  covered  by  inverted  funnels  or  by  other  cov- 
ers, flasks,  beakers  and  various  other  cylindrical  vessels — all  these 
are  good  boiling-vessels,  but  poor  evaporating-vessels. 

117  Evaporation-vessels.  The  shallow  dishes,  kettles,  or 
pans  employed  for  the  vaporization  or  evaporation  of  liquids 


EVAPORATION. 


67 


should  be  made  of  materials  which  are  sufficiently  good  conductors 
of  heat,  not  affected  by  the  substances  with  which  they  must 
come  in  contact,  and  strong  enough  to  resist  fracture. 

The  most  common  materials  are  porcelain,  other  earthenware, 
glass,  iron,  tinned  iron,  pure  tin,  copper,  tinned  copper,  enameled 
iron,  silver,  platinum  and  aluminum. 

Silver  dishes  are  very  desirable  in  cases  in  which  high  tem- 
peratures are  safe  and  the  metal  not  attacked  by  the  liquids 
heated. 

Porcelain  dishes  which  can  bear  sudden  changes  of  temperature 
without  danger  of  fracture  are  the  most  generally  useful  evap- 
orating dishes. 

But  hot  glass  and  porcelain  vessels  should  never  be  put  on  cold 
or  wet  surfaces ;  it  is  better  to  let  them  cool  gradually,  or  to  put 
them  upon  rings  of  straw, 
or  grommets  of  rubber 
tubing,  or  upon  dry  cloths, 
tow  or  cotton. 

Glass  and  porcelain  ves- 
sels should  not  be  heated 
too  suddenly,  and  should 
be  dry  on  the  outside  when 
dry  heat,  as  the  bare  flame, 
is  applied  to  them.  Wire 
gauze,  or  wire  cloth,  or  a 
sand  bath,  or  other  baths, 
may  be  interposed  be- 
tween the  flame  and  the 
glass  or  porcelain,  so  as  to 
distribute  the  heat  evenly  over  the  whole  bottom  of  the  vessel. 
The  flame  should  also  be  well  regulated  so  as  to  be  not  unneces- 
sarily high,  and  so  that  the  heat  may  be  applied  gradually. 

A  complete  assortment  of  sizes  of  porcelain  evaporating  dishes 
is  necessary  to  every  well-equipped  pharmaceutical  laboratory 
for  the  production  of  chemicals — from  50  millimeters  to  400  or 
500  millimeters  diameter. 

Metal  vessels,  except  silver,  are  rarely  useful  for  chemical 
work,  and  enameled  iron  (agateware,  etc.)  is  not  reliable  as  the 
enamel  is  too  liable  to  crack  off  or  to  become  perforated  by  "pin 
holes." 


Fig.  50.  Round-bottomed   evaporation  dish 
of  porcelain. 


Fig.  51.  Flat-bottomed  evaporation  dish  of 
porcelain. 


68 


EVAPORATION. 


118.  Modes    of    application    of    heat    for    the    evaporation 
or  vaporization  of  liquids.     According  to  the    temperature  re- 
quired the  heat  may  be  applied :    i,  by  direct  flame ;  2,  with  but  a 
piece  of  wire  cloth  interposed  between  the  flame  and  the  vessel; 
3,  by  the  sand  bath ;  4,  through  asbestos  cloth ;  5,  by  the  glycerin- 
bath,  or  an  oil-bath,  or  various  salt  solution  baths ;  6,  by  direct 
steam;  7,  by  steam  jackets;  8,  by  steam  coils  in  or  around  the 
vessel;  9,  by  the  water-bath;  or  10,  by  a  hot  air  bath. 

The  student  is  referred  to  the  chapter  on  heating  apparatus 
for  further  information  on  this  subject. 

119.  Dangers  of  over-heating  in  the  evaporation  of  solutions. 
The  temperature  can  generally  be  easily  controlled  by  means  of 
baths,  with  the  aid  of  thermeters,  by  the  regulation  of  the  flame 
or  fire,  by  gradual  elevation  of  the  temperature,  and  by  watching 
the  operation.     Should  there  be  any  signs  of  danger,  prompt 

removal  of  the  flame  or  heater,  or  of  the  vessel 
from  the  source  of  heat,  is  necessary. 

Vacuum-pans  are  much  employed  in  the  evap- 
oration of  solutions  of  organic  substances,  but 
not  in  the  operations  of  inorganic  pharmaceutical 
chemistry. 

When  water-solutions  are  evaporated  very 
high  heat,  up  to  the  boiling  point,  may  be  safely 
applied  in  many  cases  so  long  as  the  solutions 
are  dilute,  but  it  must  be  remembered  that  as  the 
density  of  the  solution  increases  the  boiling  point 
also  rises,  and  the  danger  point  may  be  reached 
unless  the  thermometer  is  used  as  a  guide. 

If  solid  matter  separates  from  the  liquid  during  the  process 
of  evaporation,  constant  stirring  is  generally  necessary  to  prevent 
accidents ;  should  the  solid  matter  form  a  pellicle  over  the  liquid, 
the  temperature  might  then  rise  too  high,  and  if  the  solid  mat- 
ter deposits  on  the  bottom  of  the  dish  the  latter  may  crack  or 
the  deposited  matter  may  become  overheated. 

The  stirrers  used  may  be  of  glass,  porcelain,  wood,  or  other 
suitable  material.  They  may  be  in  the  shape  of  rods,  spatulas, 
spoons,  or  ladles. 

120.  Slow  evaporation  may  be  performed  over  a  well  regulated 
steam-bath,  water-bath,  sand-bath, or  air-bath,  in  the  drying  closet, 
or  by  spontaneous  evaporation  without  any  application  of  heat. 


Fig.  52.  Porcelain 
stirrers. 


EVAPORATION.  69 

The  evaporating  dish  should  be  loosely  covered  with  paper,  or 
should  be  placed  under  a  hood  to  protect  the  contents  from  the 
dust. 

121.  When  objectionable  vapors  pass  off  from  evaporating 
liquids  the  employment  of  hoods  or  fume  chambers  is  necessary 
unless  it  be  found  practicable  to  carry  on  the  operation  out  of 
doors,  in  which  case  the  operator  may  easily  avoid  the  gases  by 
standing  with  his  back  to  the  quarter  from  which  the  wind  comes. 

122.  Expulsion  of  hygroscopic    moisture.     Small  amounts  of 

water  held  by  hygroscopic  sub- 
stances which  can  not  safely 
be  exposed  to  heat  may  be  re- 
moved by  means  of  desiccators 
which  consist  of  glass  covers 
placed  over  vessels  containing 
calcium  chloride,  sulphuric 
acid,  dry  potassium  hydroxide, 
dry  lime,  or  other  substances 
having  a  great  avidity  for 
water.  The  dishes,  beakers, 
watch-crystals,  or  other  ves- 

Fig.  53.  Desiccating  apparatus.  ^    CQntaining    the    substance 

or  solution  to  be  subjected  to  desiccation  are  placed  immediately 
over,  or  below,  or  beside  the  vessel  containing  the  calcium  chloride 
or  other  substance  employed  to  absorb  the  water  as  it  evaporates. 


CHAPTER  VIII. 

DISTILLATION. 

123.  Distillation  is  the  vaporization  of  a  liquid  in  an  appar- 
atus so  constructed  that  the  vapor  which  is  formed  in  one  vessel 
is  conducted  into  another  vessel  in  which  it  is  condensed  back  to 
the  liquid  state  and  collected. 

The  object  of  distillation  is  the  separation  of  volatile  liquids 
from  non-volatile  substances  with  which  they  are  mixed,  or  which 
they  contain  in  solution ;  or  the  separation  of  more  volatile  from 
less  volatile  liquids. 

The  liquids  subjected  to  distillation  may  be  mixtures  or  solu- 
tions consisting  of  two  or  more  liquids ;  or  solutions  of  substances 
which  are  solids  when  separated  from  the  solvent ;  or  mixtures  of 
solid  and  liquid  substances  not  forming  solutions ;  or  liquids  con- 
taining comparatively  small  proportions  of  other  substances  which 
it  is  desired  to  separate. 

124.  Many    different    substances   have    different    degrees   of 
volatility  within  the  range  of  temperatures  produced  in  ordinary 
distillation,  while  other  substances  are  quite  non-volatile  at  those 
temperatures. 

The  volatile  liquid  carried  over  by  the  distillation  forms  the 
product  called  the  distillate.  The  less  volatile  or  non-volatile 
matter  left  in  the  vessel  in  which  the  vaporization  was  effected 
is  called  the  residue.  This  residue  may  be  either  liquid  or  solid. 

The  separation  of  a  volatile  liquid  from  an  altogether  non- 
volatile substance  with  which  it  may  be  associated  by  solution  or 
otherwise  is  easily  effected  by  distillation. 

But  the  separation  of  two  or  several  more  or  less  volatile  liquids 
from  each  other  by  distillation  is  difficult,  and  scarcely  possible 
unless  their  respective  boiling  points  differ  sufficiently.  Such  a 
separation  is  called  fractional  distillation. 

125.  The  latent  heat  of  vapor  is  the  quantity  of  heat  required 
to  hold  it  in  its  gaseous  state.    It  is  called  "latent"  because  it  does 
not  register  upon  the  thermometer  or  reveal  itself  in  any  other 
way  than  by  performing  the  work  of  keeping  the  molecules  of  the 
volatile  substance  apart  from  each  other  so  as  to  hold  them  in 

70 


DISTILLATION.  7 1 

the  condition  constituting  what  is  known  as  "vapor,"  and  the 
energy  required  to  do  that  work  can  not  at  the  same  time  do  any 
other  work. 

The  latent  heat  of  water  vapor  or  steam  is  about  537°  C,  for 
the  amount  of  heat  energy  which  is  necessary  to  convert  i  Gram 
of  water  into  vapor  (or  to  evaporate  i  Gm  of  water)  is  precisely 
the  same  as  the  heat  energy  required  to  raise  the  temperature  of 
537  Grams  of  water  one  degree  (centigrade). 

The  latent  heat  of  alcohol  vapor  is  expressed  by  about  375°; 
and  that  of  ether  by  about  163°  C. 

The  quantity  of  heat  energy  required  to  raise  the  temperature  of 
a  given  quantity  of  water  from  o°  to  100°  C.  is  a  constant  quan- 
tity, and  the  quantity  of  heat  energy  required  to  convert  water  of 
100°  into  vapor,  and  to  hold  it  in  a  state  of  vapor,  is  5.37  times 
as  great  as  the  quantity  of  heat  energy  required  to  raise  the  tem- 
perature of  the  same  amount  of  water  100°.  The  quantity  of  heat 
energy,  or  thermal  energy,  is  measured  in  units  which  stand  for 
the  amount  of  heat  required  to  raise  the  temperature  of  one  liter 
of  water  one  degree  (centigrade).  The  quantity  of  heat  energy 
required  to  raise  the  temperature  of  one  liter  of  water  from  o° 
to  1 00°  C.  is,  therefore,  100  heat  units,  or  thermal  units.  But  the 
quantity  of  heat  energy  required  to  convert  one  liter  of  water  at 
100°  into  vapor,  and  keep  it  in  a  state  of  vapor,  is  537  thermal 
units.  Hence  637  units  of  thermal  energy  will  be  required  to  con- 
vert one  liter  of  o°  into  water  vapor  of  100°. 

Whenever  the  vapor  produced  by  one  liter  of  water  is  con- 
densed or  converted  from  vapor  at  100°  into  liquid  water  at  the 
same  temperature,  the  latent  heat  of  that  vapor,  amounting  to 
537  units,  is  released. 

126.  The  most  common  method  of  causing  the  condensation  of 
vapor  in  distillation  is  to  conduct  the  vapor  through  tubes  sur- 
rounded by  water  of  the  ordinary  temperature  (between  15° 
and  20°  C.).  This  water  is  called  the  condensing-ivater,  and  it 
serves  the  important  purpose  of  absorbing  the  heat  given  up  by 
the  vapor.  The  vapor  can  not  be  condensed  unless  its  latent 
heat  be  transferred  to  or  absorbed  by  the  substances  with  which 
it  comes  in  contact ;  but  the  rate  at  which  condensation  takes 
place  is  in  direct  proportion  to  the  rate  of  absorption  of  the  latent 
heat  of  the  vapor  by  the  vessel  in  which  it  is  condensed,  by  the 
water  surrounding  that  vessel,  and  by  the  contiguous  air. 


72  DISTILLATION. 

The  greater  part  of  the  heat  lost  by  the  vapor  is  taken  up  by 
the  condensing  water.  The  heat  lost  in  cooling  is  precisely  the 
same  amount  as  is  required  to  raise  the  same  body  through  the 
same  number  of  degrees.  If  one  kilogram  of  water  at  10°  be 
mixed  with  the  same  quantity  of  water  at  90°,  the  equalization  of 
temperature  would  result  in  two  kilograms  of  water  of  50°,  for 
the  amount  of  heat  gained  by  the  water  of  10°  would  be  one- 
half  of  the  difference  between  10°  and  90°,  and  the  heat  lost 
by  the  water  of  90°  would  be  the  other  half  of  that  difference. 

If  it  be  assumed  that  all  of  the  latent  heat  of  the  steam  in  the 
distillation  of  water  is  transferred  to  the  condensing  water,  and 
that  all  of  the  condensing  water  enters  the  condenser  at  a  tem- 
perature of  15°  and  is  heated  to  70°,  running  off  at  that  tempera- 
ture, and  if  it  be  further  assumed  that  the  distillate  passes  out 
having  a  temperature  of  80°,  then,  as  the  latent  heat  of  water 
vapor  is  537  thermal  units,  it  follows  that  about  10.74  liters  of 
condensing  water  will  be  required  to  take  up  the  latent  heat  given 
up  in  the  formation  of  one  liter  of  distilled  water,  and  nearly 
0.25  liter  of  additional  water  of  15°  will  be  required  to  reduce  the 
temperature  of  that  distillate  from  100°  to  80°,  so  that  about 
ii  liters  of  water  of  15°  would  have  to  be  supplied  to  the  con- 
denser in  making  each  liter  of  distilled  water  of  80°.  But  in 
actual  practice  the  amount  of  condensing  water  required  is  about 
twice  as  great,  for  it  is  impossible  to  regulate  the  operation  and 
prevent  waste.  All  that  can  be  done  in  this  direction  is  to  see 
that  the  condensing  water  supplied  runs  off  nearly  as  hot  as  the 
distillate  itself. 

127.  Boiling  points  of  mixed  liquids.     When  a  mixture  of  sev- 
eral liquids  of  different  boiling  points  is  heated,  it  boils  at  a 
temperature  somewhat  higher  than  the  boiling  point  of  the  most 
volatile  constituent  of  the  mixture. 

128.  Use  of  thermometers  in  distillation.     In  order  to  regulate 
the  temperature  in  distillation,  whenever  necessary,  the  mercury 
thermometer  is  often  brought  into  requisition.     The  slender  spe- 
cial laboratory  thermometer  of  glass  used   for  this  purpose   is 
represented  by  Fig.  54.     It  is  long,  of  very  fine  bore,  and  has  a 
very  small  bulb.     Such  thermometers  range  from  about  — 35° 
to  -{-200  C,  but  for  ordinary  purposes  the  most  useful  are  those 
which  register  temperatures  from  — 20°  to   100°.     Well  made 


DISTILLATION.  73 

laboratory  thermometers  do  not  break  easily,  are  not  easily  frac- 
tured by  heat,  and  may  be  conveniently  inserted  in  stills,  flasks, 
retorts,  and  other  vessels  by  means  of  perforated  rub- 
ber stoppers  or  corks. 

129.  Simple  distillation   is  exemplified  in  the  pro- 
duction  of  distilled  water,  which  is   fully  described 
elsewhere  in  this  book. 

Chemical  distillation  is  the  production  of  a  volatile 
liquid  by  chemical  reaction  and  the  separation  of  that 
product  from  the  bye-product  by  distillation,  the  reac- 
tion being  effected  in  the  distilling  apparatus. 

130.  Distilling  apparatus.     Large   stills   are  made 
of  copper,  iron,  tinned  iron,  lead  or  stoneware.    Small 
stills,  having  a  capacity  of  from  5  to  100  liters,  may 
well  be  made  of  the  same  materials. 

The  best  stills  are  usually  those  of  the  most  simple 
construction,  which  can  be  readily  cleaned  and  are  not 
liable  to  get  out  of  order. 

Glass  flasks  and  retorts  are  used  for  small  opera- 
tions. Porcelain  retorts  or  stills  are  also  occasionally 
used. 

Distilling  flasks  must  be  of  the  best  Bohemian  glass, 
of  good  shape,  thin,  not  of  uneven  thickness,  well  an- 
nealed. The  necks  of  distilling  flasks  are  sometimes 
required  to  be  rather  long,  but  more  frequently  short.  Laboratory 

A  retort  is  practically  a  flask  with  a  long  neck  bent     ter.mome~ 
at  an  angle  of  about  eighty  degrees  to  the  body.    The 
most  useful  glass  retorts  are  those  having  one  or  two  tubulures 
or  necks  with  ground  glass  stoppers. 

The  distilling  apparatus  also  includes  a  condenser  and  a  re- 
ceiver. It  is  often  practicable  to  combine  condenser  and  receiver, 
for  when  comparatively  small  amounts  of  liquid  are  distilled  and 
the  product  is  not  too  volatile  the  receiver  may  also  serve  as  the 
condenser. 

Glass  receivers  are  usually  globe-shaped,  with  wide  necks,  as 
shown  in  Fig.  55.  When  fitted  to  retorts  without  the  interven- 
tion of  condensers  they  may  be  placed  in  cold  water  or  in  broken 
ice,  or  a  stream  of  cold  water  may  be  kept  running  upon  them. 
The  necks  of  retorts  and  receivers,  or  the  tube  connecting  them, 
may  be  covered  by  a  wet  cloth  kept  cool  by  running  water. 


74 


DISTILLATION. 


Retorts  are  always  of  awkwaru  shape,  and  their  liability  to 
breakage  lessens  their  usefulness.  Flasks  are  to  be  preferred 
whenever  practicable. 


Fig.  55.  Illustrating  distillation  on  a  small  scale.     The  condenser  is  a  Liebig  con- 
denser. 

The  fittings  by  which  flasks  or  retorts  are  connected  with  con- 
densers or  receivers,  or  both,  consist  of  bent  glass  tubing,  T  tubes, 
rubber  tubing,  soft  sheet  rubber,  and  per- 
forated rubber  stoppers  or  corks.  The 
whole  apparatus  should  be  securely  sup- 
ported, the  connections  instead  of  being 
rigid  should  be  somewhat  elastic  to  di- 
minish the  danger  of  breakage,  and  all 
the  joints  should  be  tight. 

The  cork-borer  is  necessary  wrhen 
corks  are  used  instead  of  rubber  stop- 
pers, and  only  the  very  best  kind  of  cork 

can  be  used.     Perforated  rubber  stoppers  of  pure  (black)  rubber 
of  all  ordinary  sizes  and  with  one,  two,  or  more  perforations  for 


Fig.  56.  A   tubulated  glass 
retort. 


r  T 


Pig.  57.  Glass  fittings  for  distilling  apparatus  and  for  gas  apparatus;  elbow, 
T  tube,   and  glass-stoppered  piece  of  tubing. 


DISTILLATION. 


75 


the  insertion  of  glass  tube  elbbws  or  T  tubes,  safety-tubes,  reflex 
condensers,  and  thermometers,  any  or  all,  can  be  obtained  from 
any  dealer  in  chemical  apparatus  and  are  so  far  superior  to  cork 
that  they  should  altogether  displace  the  latter.  (Fig.  60.) 


Fig.  58.  Thistle-tube    and    safety    tubes    for   distilling   flasks    and 
apparatus. 


Fig.  59.  Cork-borer  of  brass  tubing. 


Fig.  60.  Perforated   rubber   stoppers. 


131.  The  worm  condenser,  or  "condensing  worm,"  is  a  simple, 
common  and  effective  condensing  apparatus  employed  in  connec- 
tion with  large  stills,  especially  for  the  distillation  of  water  or  of 


76 


DISTILLATION. 


alcohol.  It  consists  of  a  spiral  block  tin  pipe  placed  in  a  tub, 
barrel  or  tank,  through  which  cold  water  flows. 

Liebig's  condenser  is  shown  in  Fig.  55.  It  is  constructed  of 
two  tubes  which  may  be  taken  apart  and  cleaned.  The  vapor 
passes  through  and  is  condensed  in  the  inner  tube,  which  is  sur- 
rounded by  the  cold  water  passing  through  the  outer  tube. 

Squibb' 's  condenser  is  a  modification  of  Liebig's.    Fig.  61. 

Mitscherlisch's  condenser  is  a  double  cylinder  placed  in  a  ves- 


Fig.  61.  Squibb's  upright  con- 
denser. 


Fig.  62.  Vertical    section    showing    construc- 
tion of  Mitscherlisch's  condenser. 


sel  of  cold  water.  The  double  cylinder  is  made  of  two  tubes 
tightly  fitted  together  at  both  ends.  The  vapor  is  condensed 
between  the  tzvo  tubes,  and  the  cold  water  passes  around  the 
outer  tube  and  through  the  inner  tube. 

132.     Stands  for  retorts,  flasks,  condensers,  etc.,  are  made  of 
iron,  or  of  iron  and  wood.     They  should  be  strong  enough,  and 


DISTILLATION. 


77 


Pig.  63.  Apparatus   stand   of  iron   for  retorts, 
flasks,  condensers,  etc. 


Fig.  64.  Iron  stand  for  funnels, 
flasks,  beakers,   etc. 


provided  with  a  sufficiently  broad  base,  heavy,  and  with  the  center 
of  gravity  in  that  base. 


CHAPTER    IX. 

CRYSTALS    AND    CRYSTALLIZATION, 

133.  A  crystal  is  a  naturally  formed  geometric  solid  bounded 
by  smooth  plane  faces  meeting  each  other  to  form  straight  edges 
and  solid  angles.    The  edges  are  formed  by  two  contiguous  inter- 
secting faces ;  the  solid  angles  or  corners  are  formed  by  three  or 
more  faces  intersecting  each  other  at  one  point. 

Calcspar,  rock  crystal,  diamond,  galena,  alum,  blue  vitriol,  green 
vitriol,  Epsom  salt,  and  quinine  sulphate  furnish  examples  of 
crystals. 

134.  Crystallization  is  the  formation  of  crystals.    But  for  our 
present  purposes  we  shall  use  the  term  to  signify  the  preparation 
of  chemical  products  in  the  form  of  crystals. 

Crystallizable  substances  are  crystallic  when  they  occur  in  com- 
paratively well  defined,  free  or  detached  individual  crystals,  such 
as  we  see  in  alum,  copper  sulphate,  sodium  carbonate,  rock  crystal, 
and  potassium  ferrocyanide ;  they  are  crystalline  when  their  crys- 
talline structure  is  evident  throughout  their  mass,  but  the  crys- 
tals are  very  small,  imperfect,  and  not  detached  or  separable  from 
each  other,  as  in  masses  of  ferric  chloride,  black  antimony  sul- 
phide, camphor  and  ammonium  chloride. 

Substances  consisting  of  such  minute  crystals  that  they  have 
the  form  of  coarse  or  fine  powder  may  be  either  crystallic  or 
crystalline,  but  are  always  described  as  crystalline.  Powders  con- 
sisting of  minute  crystals  are  sometimes  described  as  "crystal 
meal."  When  the  crystals  are  so  small  that  they  can  not  be  recog- 
nized without  the  aid  of  the  microscope,  the  substance  made  up 
of  such  crystals  is  said  to  be  micro-crystalline. 

Substances  which  present  no  indications  of  crystalline  structure 
are  called  amorphous. 

135.  Only  molecules  of  the  same  kind  form  crystals,  or  ar- 
range themselves  into  regular  polyhedral  solid  bodies,  except  that 
water  (and  sometimes  alcohol)  of  crystallization  can  be  included. 
Hence  when  any  substance  crystallizes  into  well  defined  crystals 

78 


CRYSTALS  AND  CRYSTALLIZATION.  79 

other  substances  which  may  be  present  with  it  are  excluded,  so 
that  crystallization  is  a  good  indication  of  probable  purity. 

But  crystallization  is  not  absolute  evidence  of  purity,  for,  al- 
though it  is  true  in  a  general  way  that  crystals  are  chemically 
homogeneous  or  consist  of  but  one  kind  of  molecules,  it  hap- 
pens quite  frequently  that  other  kinds  of  molecules  are  mechani- 
cally included  in  the  crystals  formed,  or  that  the  exclusion  of  for- 
eign substances  is  not  complete  until  after  repetition  of  the  proc- 
ess of  crystallization  once,  twice,  or  several  times.  Moreover, 
there  are  some  substances  which  freely  crystallize  together  and 
the  crystals  of  which  grow  in  each  other's  solutions. 

136.  There  are  innumerable  distinctly  different  forms  of  crys- 
tals ;  but,  as  a  rule,  each  particular  kind  of  matter  crystallizes  in 
but  one  form,  so  that  the  crystal  form  of  a  substance  is  one  of  the 
means  by  which  it  may  be  identified. 

Numerous  different  substances  may,  however,  crystallize  in  the 
same  form  even  if  they  can  not  crystallize  together  to  enter  into 
the  formation  of  the  same  individual  crystals.  It  happens,  too, 
that  apparently  the  same  species  of  molecules  may  crystallize  in 
two  or  three  different  forms. 

137.  Substances  crystallizing  in  two  different  forms  are  called 
dimorphous  substances;  those  crystallizing  in  three  forms  are 
triuiorphous  or  polymorphous. 

When  different  substances  crystallize  in  the  same  form  they 
are  said  to  be  homoeomorphous.  But  homceomorphous  substances 
are  frequently  of  altogether  dissimilar  internal  structure. 

Isomorphous  substances  have  not  only  the  same  crystalline 
form  but  also  perfectly  analogous  internal  structure.  They  gen- 
erally contain  the  same  number  of  atoms  in  their  respective  mole- 
cules ;  the  systems  of  interatomic  linking  of  any  two  or  more 
isomorphous  substances  are  identical ;  they  contain  the  same  num- 
ber of  molecules  of  water  of  crystallization,  if  any ;  they  crys- 
tallize together  in  the  same  crystals  from  a  common  solution ;  and 
their  crystals  may  grow  in  each  other's  solutions  (or  the  crystal  of 
a  less  soluble  substance  may  be  made  to  grow  in  a  more  soluble 
isomorphous  substance).  Examples  of  isomorphous  substances 
are:  the  alums  (although  an  ammonium  alum  does  not  contain 
the  same  number  of  atoms  as  the  corresponding  alum  formed  by 
any  alkali  metal)  ;  the  phosphates  and  arsenates  of  the  alkali 
metals ;  the  halides  of  the  alkali  metals ;  the  nitrates  of  potassium, 


80  CRYSTALS  AND  CRYSTALLIZATION. 

rubidium  and  caesium ;  the  carbonates  of  magnesium  and  calcium ; 
the  sulphates  of  magnesium  and  zinc ;  etc. 

Sodium  nitrate,  NaNO3,  and  calcium  carbonate,  CaCO3,  crys- 
tallize in  similar  forms,  and  their  molecules  contain  identical 
numbers  of  atoms;  but  they  are  not  isomorphous  because  their 
systems  of  atomic  linking  are  altogether  dissimilar  owing  to  the 
fact  that  sodium  is  a  monad  and  calcium  a  dyad,  and  that  the 
nitrogen  of  NaNO3  is  a  pentad,  while  the  carbon  of  the  CaCO3 
is  a  tetrad — 

J>  /°\ 

Na— O— Nf  Ca/      C=O 

T>  ^0' 

Sodium  nitrate  and  calcium  carbonate  are  accordingly  only 
homoeomorphous. 

Elements  having  different  valences  can  not  replace  each  other 
and  form  isomorphous  substances. 

Different  substances  which  crystallize  in  different  forms  are 
heteromorphous.  They  never  crystallize  together  in  the  same 
identical  crystals. 

When  heteromorphous  substances  are  contained  together  in 
the  same  solution  they  may  be  separated  from  each  other  by 
crystallization,  especially  if  their  respective  solubilities  differ  suf- 
ficiently;  but  isomorphous  substances  are  difficult  to  separate 
in  this  way,  even  if  they  do  not  freely  enter  into  the  formation 
of  the  same  individual  crystals. 

Less  soluble  substances,  of  course,  crystallize  before  the  more 
soluble  substances  from  the  same  solution. 

But  the  presence  of  two  or  more  substances  in  the  same  solu- 
tion may  cause  one  of  these  substances  to  form  crystals  having  the 
form  belonging  to  the  other  or  one  of  the  others.  For  instance, 
copper  sulphate  crystallizes  normally  in  the  triclinic  form,  but  if 
it  crystallizes  from  a  solution  containing  about  one-seventh  as 
much  ferrous  sulphate  as  copper  sulphate,  the  copper  salt  will 
crystallize  in  monoclinic  prisms,  the  form  of  the  crystals  of  fer- 
rous sulphate. 

138.  General  descriptive  terms,  referring  to  the  forms  of  crys- 
tals, are  so  numerous  that  they  can  not  be  mastered  without  a 
more  extended  study  of  crystallography  than  is  possible  in  this 
book. 


CRYSTALS  AND  CRYSTALLIZATION. 


8l 


The  axes  of  crystals  are  the  several  directions  of  their  exten- 
sion. As  geometric  solids  must  have  at  least  three  directions  of 
extension — length,  breadth  and  thickness — it  follows  that  no  crys- 
tal can  have  less  than  three  axes ;  but  crystals  of  the  hexagonal 

CRYSTALLINE    FORMS    OF    THE    REGULAR   SYSTEM. 


Fig.  65.     Regular  octohedron. 


Fig.  66.  Cube. 


Fig.    67.    Rhombic   dodcka- 
hedron. 


system  have  four  axes.  The  forms  of  crystals  depend  primarily 
upon ;  i,  the  number  of  the  axes;  2,  the  angles  at  which  the  axes 
severally  intersect  each  other,  and  3,  the  respective  lengths  of  the 
several  axes  with  regard  to  each  other.  All  the  crystalline  forms 
are  grouped  into  six  distinct  systems,  called : 


CRYSTALLINE  FORMS  OF  THE  HEXAGONAL  SYSTEM. 


Fig.  68.  Double   six-sided 
pyramid. 


Fig.  69.  Six-sided  prism.       Fig.  70.    Hexagonal 
pyramidal  prism. 


I.  The  Regular  System  (monometric,  tessular,  or  cubic  sys- 
tem).— Crystals  having  three  axes  of  equal  length  intersecting 
each  other  at  right  angles.  The  facial  angles  or  edges  are,  there- 
fore, also  right  angles. 

Vol.    II— 6 


82 


CRYSTALS  AND  CRYSTALLIZATION. 


The  fundamental  forms  of  this  system  are  the  cube,  the  regu- 
lar octohedron,  and  the  rhombic  dodekahedron. 

II.     The   Hexagonal   System    (rhombohedral    system). — Axes 


Fig.      71.        Hemihedral 
rhombohedron. 


Fig.  72.  Combination  of 
rhombohedron  and 
prism. 


Fig.  73.  Scalenohedron 
with  inscribed  hemi- 
dral  rhombohedron. 


CRYSTALLINE  FORMS  OF  THE  QUADRATIC  SYSTEM. 


Fig.  74.  Square-based 
double  pyramid.  (Oc- 
tohedron.) 


Fig.  75.  Quadratic  prism. 


Fig.  76.  Form  found  in 
crystals  of  the  sul- 
phates of  magnesium 
and  zinc. 


CRYSTALS  AND  CRYSTALLIZATION.  83 

four.  Three  of  these  axes  are  of  equal  length;  these  are  called 
the  secondary  axes.  The  fourth,  called  the  primary  axis,  is  either 
longer  or  shorter  than  the  other  three.  The  secondary  axes  are 
all  in  the  same  plane,  and  cut  one  another  at  angles  of  60  de- 
grees; the  primary  axis  is  at  right  angles  to  the  plane  of  the 
•  other  three. 

The  fundamental  form  of  this  system  is  the  double  six-sided 
pyramid.  Other  important  forms  are  the  regular  six-sided 
prism,  and  the  rhombohedrons. 

III.  The  Quadratic  System   (the  dimetric,  square,  prismatic, 
pyramidal  or  tetragonal  system). — Three  axes.     The  two  sec- 
ondary axes  are  of  equal  length;  the  primary  axis  is  longer  or 
shorter.    The  axial  angles  are  all  right  angles. 

Pyramids  of  this  system  have  square  bases. 
The  dominant  forms  are  the  double  four-sided,  square-based 
pyramid  and  the  right  square  prism. 

IV.  The  Rhombic  System  (trimetric,  or  right  prismatic  sys- 
tem).— The  three  axes,  all  of  unequal  lengths,  cut  each  other  at 
right  angles. 

The  fundamental  form  is  the  right  rhombic  double  pyramid,  or 
rhombic-based  octohedron. 

V.  The  Monoclinic  System  (monosymmetric  or  oblique  pris- 
matic system). — The  three  axes  are  of  unequal  length;  the  two 
secondary  axes  are  at  right  angles  to  each  other ;  the  primary 
axis  is  at  right  angles  to  one  of  the  secondary  axes,  but  forms 
oblique  angles  with  the  other. 

The  primary  form  is  the  monoclinic  pyramid. 

VI.  The  Triclinic  System  (the  assymmetric,  or  double  oblique 
prismatic  system). — The  three  axes  all  of  unequal  length,  and 
the  axial  angles  all  oblique. 

The  fundamental  form  is  the  triclinic  pyramid. 

139.     Cubes  belong  to  the  regular  system. 

Prisms  are  to  be  found  in  all  except  the  regular  system. 
Prisms  with  rectangular  sides  if  they  are  six-sided  belong  to 
the  hexagonal  system  ;  they  belong  to  the  quadratic  system  if  four- 
sided  and  square-based.  Prisms  with  oblique  angles  or  rhomboid 
sides  and  bases  belong  to  the  monoclinic  system  if  any  two  of 
their  axes  are  at  right  angles;  but  to  the  triclinic  system  when 
they  have  no  right  axial  angles.  Prisms  of  the  rhombic  system 
have  rectangular  but  not  square  bases. 


84 


CRYSTALS  AND  CRYSTALLIZATION. 


Pyramids  belong  to  all  the  six  systems.  Those  with  square 
bases  belong  to  either  the  regular  or  to  the  quadratic  system ;  if 
their  faces  are  equilateral  triangles  they  belong  to  the  regular 
system,  but  they  belong  to  the  quadratic  system  if  their  faces  are 
isoceles  triangles.  Pyramids  of  the  hexagonal  system  have 
hexagonal  bases,  and  their  faces  are  isoceles  triangles.  Pyra- 


Fig.    77.     Truncated   oc-  Fig.  78.  Quadratic  prism        Fig.   79.     Stannic   oxide, 

tohedron.      (Potassium  with  pyramidal  ends, 
ferrocyanide.) 

CRYSTALLINE  FORMS   OF   THE   RHOMBIC   SYSTEM. 


Fig.  80.  Rhombic  double 
pyramid.     (Octohedron.) 


Fig.  81.  Rhombic  prism 
with  pyramidal  ends. 
(Zinc  sulphate.) 


Fig.  82.  Rhombic  pyra- 
midal prism.  (Potas- 
sium sulphate.) 


mids  with  rhombic  or  rhomboid  bases  belong  to  the  rhombic  sys- 
tem if  all  the  axes  are  at  right  angles ;  to  the  monoclinic  system 
if  any  two  axes  are  at  right  angles,  but  not  all ;  and  to  the  tri- 
clinic  system  when  there  are  no  right  axial  angles. 

Tetragons  have  four  angles  or  corners ;  hexagons  six ;  octagons 
eight,  etc. ;  tetrahedrons  have  four  sides ;  hexahedrons  six ;  octa- 
hedrons eight ;  dodekahedrons  twelve,  etc. 

140.  Some  substances  crystallize  with  water ;  others  without 
"water  of  crystallization."  Hydrous  crystals  are  those  containing 
water;  anhydrous  crystals  do  not  contain  it. 


CRYSTALS  AND  CRYSTALLIZATION. 


Hydrous  crystals  may,  however,  be  quite  dry  in  the  sense  that 
they  do  not  contain  any  moisture  on  their  surface.  On  the  other 
hand,  anhydrous  crystals  may  contain  small  quantities  of  inter- 
stitial water  imprisoned  between  the  individual  small  crystals  of 
which  larger  crystals  always  consist.  Crystals  containing  inter- 
stitial water  decrepitate  or  burst  with  a  slight  explosion  when 
heated. 

CRYSTALLINE  FORMS  OF  THE  MONOCLINIC  SYSTEM. 


Fig.  83.  Monoclinic  dou-       Fig.  84.  Morioc'inic  prism 
ble    pyramid.  of  sodium  acetate. 


Fig.  85.  Monoclinic  prism 
of  cane  sugar. 


CRYSTALLINE   FORMS  OF  THE  TRICLINIC   SYSTEM. 


Fig.  86.    Triclinic  pyr- 
amid (gypsum). 


Fig.    87.     Triclinic 
prism. 


Fig.  88.  Triclinic  prism 
of  calcium  thiosul- 
phate. 


141.  The  water  of  crystallization  is  held  by  molecular  attrac- 
tion, it  is  essential  to  the  crystalline  form  of  hydrous  crystals, 
and  is  always  a  molecular  proportion. 

The  proportion  of  water  of  crystallization  of  salts  varies  from 
$%  to  60%. 

Hydrous  crystals  are  generally  formed  in  water-solutions  of 
the  crystallizing  substances,  and  some  salts  take  up  varying  pro- 
portions of  water  of  crystallization  according  to  the  degree  of 


86  CRYSTALS  AND  CRYSTALLIZATION. 

concentration  of  the  solutions.  Crystals  are,  of  course,  formed 
only  in  saturated  or  supersaturated  solutions,  and  the  strength  of 
a  saturated  salt-solution  depends  upon  its  temperature.  Crystals 
formed  in  hot  (and,  therefore,  stronger)  solutions  generally  take 
up  less  water  than  those  formed  in  cold  solutions. 

Manganous  sulphate  crystallized  from  a  solution  saturated  at  or 
below  6°  contains  seven  molecules  of  water;  crystallized  from  a 
solution  saturated  at  from  7°  to  20°  it  contains  five  molecules ;  at 
20°  to  30°  it  crystallizes  with  only  four  molecules  of  water. 

Sodium  phosphate  crystallizes  with  twelve  molecules  of  water 
at  about  30° ;  but  with  only  seven  molecules  from  a  solution  sat- 
urated at  40°. 

Sodium  carbonate  crystallizes  with  either  ten,  nine,  seven,  or 
five  molecules  of  water  of  crystallization  according  to  the  tem- 
perature and  strength  of  the  solutions. 

Copper  sulphate  generally  crystallizes  with  five  molecules  of 
water.  But  if  an  effloresced  crystal  of  nickel  sulphate  be  added  to 
a  supersaturated  solution  of  copper  sulphate,  crystals  of  the  cop- 
per salt  containing  six  molecules  of  water  are  deposited.  If,  on 
the  other  hand,  a  crystal  of  ferrous  sulphate  be  added  instead  of 
nickel  sulphate,  the  crystals  of  copper  sulphate  obtained  will  con- 
tain seven  molecules  of  water. 

Zinc  sulphate  crystallized  at  the  ordinary  room  temperature,  or 
at  any  temperature  below  30°,  contains  seven  molecules  of  water; 
but  crystals  formed  at  over  30°  contain  only  five  molecules. 

These  facts  emphasize  the  necessity  of  regulating  the  tempera- 
ture and  degree  of  concentration  of  solutions  from  which  sub- 
stances are  to  be  crystallized. 

142.  Salts  containing  water  of  crystallization  do  not  always 
hold  all  of  that  water  with  the  same  force. 

Magnesium  sulphate  gives  up  one  molecule  of  water  when  dried 
at  30°  to  52°  ;  .at  water-bath  heat  it  loses  four  additional  mole- 
cules ;  and  at  a  still  higher  temperature  it  is  rendered  anhydrous. 

Potash  alum  contains  about  45.6  per  cent  of  water  of  crystalliza- 
tion ;  heated  at  40°  it  gives  up  2.7  per  cent  of  that  water ;  at  47° 
it  loses  9.6  per  cent ;  at  60°  it  loses  most  of  its  water ;  but  long 
continued  heating  at  100°  is  necessary  to  expel  all. 

Crystallized  ferrous  sulphate,  FeH2SO5.6H2O,  gives  up  nearly 
all  of  its  six  molecules  of  water  of  crystallization  at  from  90°  to 


CRYSTALS  AND  CRYSTALLIZATION.  87 

iOO°  ;  but  it  begins  to  give  off  some  of  it  even  at  the  ordinary  tem- 
perature of  the  air. 

Sodium  phosphate,  containing  twelve  molecules  of  water,  loses 
five  molecules  of  that  water  at  40°  to  50° ;  all  of  it  at  100°. 

Efflorescence  means  the  loss  of  crystalline  form  through  the  loss 
of  the  water  of  crystallization,  the  crystals  falling  to  powder. 

Hydrous  crystals  are  frequently  efflorescent,  but  rarely  deliques- 
cent. 

Solids  which  neither  effloresce  nor  deliquesce  are  described  as 
"permanent  in  the  air." 

The  solution  of  hydrous  crystals  in  their  own  water  of  crystal- 
lization is  called  aqueous  fusion. 

143.  The  objects  of  crystallization  are:     I,  the  separation  of 
crystallizable  substances  from  amorphous  substances  when  they 
occur  together  in  one  solution.     (This  separation  can  also  be  ef- 
fected by  dialysis)  ;  2,  the  separation  of  heteromorphous  substances 
from  each  other  when  together  contained  in  one  solution;  3,  the 
purification  of  commercial  chemicals ;  4,  improvement  of  the  ap- 
pearance of  the  products. 

144.  Crystals  are  most  readily  formed  when  crystallizable  sub- 
stances pass  from  the  liquid  or  the  gaseous  condition  to  the  solid 
state,  for  the  molecules  of  fluids  are  more  mobile  than  those  of 
solids,  and  the  formation  of  crystals  is  the  arrangement  of  the 
molecules  into  solids  of  definite  form  according  to  the  nature 
of  each  individual  crystallizing  substance. 

But  crystallization  nevertheless  does  take  place  even  in  solids 
which  thus  become  changed  from  the  amorphous  to  a  crystalline 
condition.  Some  metals  are  known  to  undergo  this  change ;  also 
arsenous  oxide,  melted  sugar,  etc. 

145.  Methods  of  effecting  crystallization.     The  usual  means 
of  inducing  solids  to  assume  the  crystalline  form  are :    I,  insoluble 
but  fusible  crystallizable  solids  are  liquefied  by  fusion  and  then 
allowed  to  cool  slowly  (par.  29)  ;  2,  volatile  crystallizable  solids 
may  be  crystallized  by   sublimation ;   3,   soluble   substances  are 
crystallized  by  deposition  out  of  their  solutions ;  4,  some  liquids 
are  crystallized  by  freezing   (for  purposes  of  purification),  as, 
e.  g.,  glycerin,  chloroform,  etc.   (Pictet's  process)  ;  and  5,  many 
insoluble,  or  very  sparingly  soluble,  substances  are  obtained  in 
minute  crystals  when  produced  by  precipitation. 


CHAPTER  X. 

CRYSTALLIZATION    FROM    SOLUTIONS. 

146.  The  most  common  and  successful  method  of  crystalliza- 
tion is  that  of  soluble  solids  by  inducing  them  to  form  crystals 
from  their  solutions. 

Any  crystallizable  soluble  solid  may  be  comparatively  easily 
crystallized  from  its  solution,  unless  the  substance  is  so  extremely 
freely  soluble  as  to  be  nearly  or  quite  deliquescent. 

A  crystallizable  substance  separates  from  its  solution  in  the 
form  of  crystals  whenever  the  amount  of  solvent  present  is  insuf- 
ficient to  retain  all  of  it  in  solution. 

The  ratio  of  solubility  of  a  given  solid  in  a  given  solvent  at 
any  given  temperature  is  a  constant  ratio.  A  saturated  solution 
of  a  crystallizable  substance,  therefore,  must  deposit  crystals 
whenever  the  proportion  of  solvent  is  diminished  by  evaporation. 

Crystals  are  also  deposited  when  the  temperature  of  a  saturated 
solution  is  lowered  if  the  crystallizable  substance  dissolved  is 
soluble  in  greater  proportion  at  a  higher  temperature. 

Crystallization  from  saturated  solutions  is,  therefore,  effected 
either,  i,  by  evaporation  of  the  solvent;  or  2,  by  reduction  of  the 
temperature  of  the  solution;  or  3,  by  both  of  these  means  together. 

147.  Water-soluble   chemical   compounds  are  generally  pro- 
duced in  a  state  of  solution,  and  are  recovered  from  their  solu- 
tions by  crystallization  if  they  are  crystallizable  solids. 

148.  The  size  of  crystals.     Some  substances  naturally  form 
large  crystals,  while  others  form  small  crystals.     But  much  can  be 
done  to  increase  or  diminish  the  size  of  crystals  formed  from 
solutions. 

If  large  and  well  developed  crystals  are  desired  their  forma- 
tion must  be  slow.  Hence  they  must  be  produced  by  very  slow 
evaporation  of  the  saturated  solution,  or  by  very  slow  cooling  of 
it.  As  experience  has  further  shown  that  large  crystals  are  more 
readily  obtained  from  weaker  solutions  than  from  stronger  ones, 
it  follows  that  the  best  plan  is  to  make  the  solution  saturated  at 
not  above  the  ordinary  laboratory  temperature  and  to  expose 

88 


CRYSTALLIZATION    FROM    SOLUTIONS.  89 

that  solution  to  spontaneous  evaporation.  Another  condition 
necessary  to  the  formation  of  large  crystals  is  perfect  rest  and 
abundant  room  for  the  crystals  to  grow  in.  Finally,  if  the  tem- 
perature of  the  solution  be  as  nearly  constant  as  possible  so  that 
spontaneous  evaporation  of  the  solvent  is  the  only  means  of  in- 
ducing the  necessary  supersaturation  which  must  precede  the 
deposition  of  crystals,  the  most  favorable  conditions  are  attained. 
Sudden  or  great  fluctuations  of  temperature  interfere  seriously 
with  the  growth  of  crystals. 

If  small  crystals  are  preferred  they  should  be  caused  to  de- 
posit quickly.  Strong  solutions,  quickly  cooled ;  rapid  evapora- 
tion or  vaporization  of  the  solvent ;  agitation  of  the  liquid — these 
means  produce  small  crystals. 

Small  crystals  (granulated  crystalline  products,  turbidated 
salts,  and  products  in  the  form  of  crystal  meal,  or  in  powder) 
are  very  convenient  because  small  quantities  of  them  can  be  very 
easily  and  accurately  weighed  and  because  they  are  quickly  sol- 
uble; but  some  substances  are  so  injuriously  affected  by  con- 
tact with  air  that  they  keep  very  much  better  in  large  crystals 
than  in  crystalline  powder. 

149.  Turbidation. — Salts  which  are  far  more  soluble  in  hot 
water  than  in  cold  water  may  be  purified  or  recrystallized  by 
making  saturated  hot  solutions  of  them  and  agitating  these  solu- 
tions during  the  process  of  cooling.  Solutions  for  this  purpose 
should  be  so  made  as  to  be  saturated  at  the  boiling  point  if 
they  do  not  require  filtration.  But  if  they  must  be  filtered,  they 
should  be  made  weaker  in  order  to  prevent  crystallization  during 
the  process  of  filtration,  unless  facilities  are  available  for  filtering 
liquids  at  the  boiling  point  of  water.  When  salt  solutions  heated 
to  the  boiling  point  are  to  be  filtered  through  paper  filters  in 
glass  funnels  it  is  best  to  make  the  solutions  of  such  strength 
that  they  are  saturated  at  about  80°  C,  and  the  funnel  used 
should  be  made  hot  by  means  of  hot  water  before  the  filter  is 
inserted  and  the  solution  poured  into  it. 

Turbidated  salts  are  crystalline,  but  the  crystals  are  small. 
Turbidation  is  the  granulation  of  water-soluble  salts  by  the 
rapid  cooling  of  hot  saturated  solutions,  the  formation  of  small 
crystals  being  insured  by  agitation  of  the  solution  and  not  by 
evaporation. 

Turbidation  is  applicable  in  the  preparation  of  small  crystals 


OO  CRYSTALLIZATION    FROM    SOLUTIONS. 

of  chlorate,  nitrate,  and  dichromate  of  potassium,  borax,  alum, 
ferrous  sulphate,  lead  acetate,  copper  sulphate,  and  many  other 
salts. 

Turbidated  salts  which  are  not  affected  by  alcohol  but  which 
do  not  bear  long  exposure  to  air  while  in  a  moist' state  should 
be  washed  with  alcohol  before  they  are  dried,  as,  for  example, 
ferrous  sulphate. 

150.  Granulation. — Water-soluble  salts  may  be  granulated  by 
evaporating   their   water-solutions   to   dryness    during   constant 
stirring  after  the  salt  has  begun  to  separate.     The  solution  must 
be  filtered  before  it  is  evaporated,  and  the  evaporation  is  carried 
on  without  much  stirring  until  a  pellicle  begins  to  be  formed  or 
until  salt  separates  on  the  dish  just  above  the  surface  of  the 
liquid;  during  the  subsequent  evaporation  the  solution  must  be 
stirred  to  prevent  the  formation  of  larger  crystals. 

Salts  containing  water  of  crystallization  can  not  be  granulated 
by  evaporation  to  dryness  because  of  the  danger  of  expelling  a 
part  of  that  water. 

In  the  evaporation  of  salts  to  dryness  it  is  necessary  to  take 
into  account  that  some  of  the  salts  of  volatile  and  comparatively 
weak  acids,  and  the  salts  of  ammonium,  may  be  partly  decom- 
posed by  the  heat.  Thus  a  solution  of  neutral  ammonium  sul- 
phate might  become  acid  during  the  progress  of  the  evaporation, 
while  a  solution  of  potassium  acetate  might  become  alkaline. 
These  difficulties  are  corrected  by  neutralization. 

Granulated  salts  are  generally  crystalline,  but  many  are  sim- 
ply granular  powders  without  crystalline  form. 

Many  halides,  citrates,  tartrates,  and  other  salts  may  be  granu- 
lated in  this  manner. 

151.  The  bulk  or  quantity  of  product  made  has  great  influ- 
ence upon  the  size  and  perfection  of  form  of  crystals,  larger  and 
finer  crystals  being  more  easily  obtained  the  greater  the  quantity 
operated  upon.     Small  quantities  of  solution  sometimes  refuse  to 
give   good   crystals   of   substances   which   crystallize   well   from 
larger  bodies  of  liquid. 

152.  When  crystallization  is  resorted  to  as  a  means  of  elimina- 
tion of  soluble  impurities,  the  process  should  be  rather  slow  and 
therefore  performed  from  solutions  saturated  at  not  above  the 
ordinary  room  temperature. 

153.  When  the  object  of  the  crystallization  is  simply  to  con- 


CRYSTALLIZATION    FROM    SOLUTIONS.  9! 

vert  an  already  pure  product  into  good  crystals,  and  the  quan- 
tity of  solid  to  be  crystallized  is  so  large  as  to  render  it  desir- 
able to  divide  it  into  two  or  more  portions,  water  is  used  as  the 
solvent  only  on  the  first  portion,  the  solutions  are  made  at  a 
somewhat  elevated  temperature,  the  crystallization  is  effected  by 
cooling,  and  the  mother-liquor  is  used  as  the  solvent  for  subse- 
quent portions  of  the  salt. 

154.  In  manufacturing  it  happens  most  frequently  that  the 
solutions  obtained  when  water-soluble  solids  are  produced  are 
rather  dilute,  or  at  all  events  not  saturated  solutions.     If  the 
product  is  to  be  crystallized  it  is  then  necessary  to  concentrate 
the  solution  by  evaporation,  or  by  "boiling  it  down." 

Solutions  of  moderately  soluble  salts  may  be  evaporated  until 
a  pellicle  forms  on  the  surface  of  the  solution,  or  until  a  small 
sample  of  the  solution  becomes  turbid  from  the  deposition  of 
small  crystals  on  cooling,  or  until  solid  particles  (crystals)  begin 
to  form  on  the  sides  of  the  vessel  near  the  level  of  the  liquid. 

Freely  soluble  salts  can  not  be  well  crystallized  from  solutions 
saturated  at  a  high  temperature. 

155.  Larger  crystals  are  usually  formed  in  turbid  solutions 
than  in  clear  ones.    But  clean,  pure  products  can  not  be  obtained 
from  dirty  solutions. 

A  powdered  crystallizable  salt  when  placed  in  a  saturated  solu- 
tion of  the  same  substance,  gradually  assumes  a  distinct  crystal- 
line form.  The  small  particles  of  salt  serve  as  nuclei  for  the 
formation  of  crystals  which  may  grow  to  a  considerable  size. 
The  size  of  crystals  may  be  increased  in  a  similar  way.  This 
is  called  nursing  the  crystals.  Gradual  changes  of  temperature 
of  the  solution  containing  an  excess  of  (undissolved)  salt  promote 
the  growth  of  the  crystals,  because  the  smallest  particles  redis- 
solve  when  the  temperature  is  increased  and  the  dissolved  salt 
deposits  on  the  surface  of  the  larger  particles  (or  crystals)  when 
the  temperature  falls. 

The  vessel  containing  the  solution  and  salt  may,  therefore, 
be  put  in  a  warm  place  occasionally  to  effect  the  result  described. 

156.  Stunted  crystals  are  generally  obtained  when  the  crys- 
tallization  progresses   too   rapidly,   for   the    numerous    crystals 
formed  simultaneously  are  apt  to  crowd  each  other.     The  same 
result  is,  of  course,  also  caused  by  contact  of  the  crystals  with  the 
bottom  and  sides  of  the  vessel. 


92  CRYSTALLIZATION    FROM    SOLUTIONS. 

157.  The  crystals  formed  may  be  either  free  (detached  from 
each  other),  and  are  then  usually  well  developed;  or  they  may 
form  clusters,  clumps,  crusts,  or  cakes. 

Detached  crystals  and  clusters  of  crystals  are  formed  in  the 
body  of  the  solution  where  they  have  room  and  freedom  to 
develop. 

Crusts  and  cakes  of  imperfect  crystallization  are  formed  on 
the  sides  and  bottom  of  the  vessel. 

To  obtain  particularly  perfect  crystals  for  the  purpose  of  ex- 
amining their  form,  a  few  crystals  may  be  slowly  nursed  to  per- 
fection in  a  small  vessel,  each  crystal  being  turned  occasionally, 
or  the  crystal  may  be  suspended  in  the  solution  by  a  thread  so  as 
to  be  free  to  develop  in  every  direction. 

When  large  quantities  of  solution  are  made  to  deposit  crys- 
tals a  mass  of  fine,  large,  free  crystals  are  usually  formed  in  the 
center,  while  crusts  are  formed  on  the  sides  and  bottom  of  the 
vessel. 

158.  Retarded    crystallization.     One    of    the    inconveniences 
attendant  upon  the  crystallization  of  salts  from  solutions  is  the 
formation  of  supersaturated  solutions  which  sometimes  refuse  to 
deposit  crystals.    This  can  generally,  but  not  always,  be  remedied 
by  dropping  some  crystals  of  the  same  salt  into  the  supersatur- 
ated solution.     When  once  started  the  crystallization  usually  con- 
tinues without  interruption. 

The  addition  of  another  salt  is  a  remedy  rarely  practicable. 

But  retarded  or  difficult  crystallization  may  sometimes  be  ad- 
vantageously prevented  by  the  very  gradual  addition  of  a  non- 
solvent  liquid  to  the  solution.  Thus,  if  some  alcohol  is  very 
cautiously  laid  over  the  surface  of  a  strong  water-solution  of  a 
substance  nearly  insoluble  or  only  sparingly  soluble  in  alcohol, 
the  water  will  gradually  absorb  the  alcohol  and  give  up  the  salt 
which  then  crystallizes  if  the  process  is  slow  enough. 

Substances  crystallizing  with  a  large  amount  of  water  of  crys- 
tallization sometimes  fail  to  form  crystals  when  the  solutions  are 
too  strong,  or  when  the  required  amount  of  water  is  not  present, 
as  is  the  case  with  ferric  chloride. 

159.  Crystallizers.     The   vessels   in   which    crystallization   is 
effected  are  called  crystallizers.     They  may  be  deep  if  the  crys- 
tallization is  to  be  induced  by  lowering  the  temperature  of  the 


CRYSTALLIZATION    FROM    SOLUTIONS.  93 

saturated  solution.     But  if  the  crystallization  is  to  be  effected 
by  spontaneous^  evaporation  the  crystallizer  should  be  shallow. 

Experience  has  shown  that  when  large  quantities  are  operated 
upon,  angular  crystallizers  and  those  with  a  comparatively  rough 
interior  surface  are  preferable  to  smooth,  spherical  vessels. 
Glass  and  glazed  porcelain 
are,  therefore,  not  always 
the  best  materials  out  of 
which  crystallizers  are  made. 
Circular  or  rectangular  flat- 
bottomed  dishes  of  glass  and 
of  porcelain  are  very  good 
for  small  operations,  but 

Fig.  89.  Crystallizer    of    glass. 

large   crystallizers  are  made 

of  wood,  rough  earthenware,  iron,  and  other  material  according  to 

the  nature  of  the  substances  to  be  crystallized  in  them. 

160.  Points  of  attachment  for  the  crystals  are  useful  if  the 
crystallization  requires  to  be  hastened  by  such  means,  as  when 
the  crystals  are  to  be  made  of  large  size  and  the  process  is  ac- 
cordingly otherwise  slow. 

Just  as  crystallizers  with  angles  or  corners,  or  with  a  rough 
interior,  are  advantageous  for  facilitating  crystallization,  so  are 
sticks,  strings,  or  wires  placed  in  the  liquid  an  excellent  means 
to  the  same  end,  whenever  their  introduction  is  admissible.  Rock 
candy,  ferrous  sulphate,  copper  sulphate,  and  potassium  ferro- 
cyanide  are  crystallized  on  a  large  scale  in  that  way. 

161.  Mother  liquors.     The  saturated  solution  remaining  at  the 
end  of  the  deposition  of  crystals,  and,  in  fact,  the  liquid  in  which 
any  crystals  are  formed,  is  called  the  mother  liquor. 

When  the  solution  contains  a  perfectly  pure  salt,  the  only  ob- 
ject being  the  recovery  of  that  salt  or  its  conversion  into  crystals, 
the  mother-liquor  is,  of  course,  generally  still  a  solution  of  pure 
salt  at  the  end  of  the  process.  But  if  the  mother-liquor  is 
evaporated  from  time  to  time  with  the  aid  of  heat,  the  last  mother- 
liquor  may  not  be  free  from  impurities,  for  the  heat  may  cause 
more  or  less  decomposition,  as  it  usually  does  in  the  concentration 
of  consecutive  mother-liquors  obtained  in  the  crystallization  of 
organic  substances  (for  instance,  citrates,  tartrates,  alkaloidal 
salts,  etc.). 

162.  Whenever  the  crystallization  is  effected  by  the  cooling  o£ 


c;4  CRYSTALLIZATION    FROM    SOLUTIONS. 

solutions  made  saturated  at  an  elevated  temperature,  and  the 
mother-liquor  after  each  crystallization  is  concentrated  by 
evaporation  with  the  aid  of  heat,  several  crops  of  crystals  are 
obtained — one  from  each  operation.  In  all  such  cases  the  prob- 
able result  will  be  that  the  first  crop  is  better  than  any  subse- 
quent one,  and  that  the  last  crop  is  poorer  than  the  preceding  ones. 

163.  Whenever  crystallization  is  performed  for  the  purpose 
of  purifying    the  substance  to  be    crystallized,  each  successive 
mother-liquor  must  contain  an  increasing  proportion  of  the  im- 
purities, and  each  successive  crop  of  crystals  must  be  more  and 
more  liable  to  be  impure,  until  finally  the  end-mother-liquor  is 
reached  from  which  a  product  fit  for  use  without  further  purifica- 
tion can  not  be  obtained. 

Usually  only  three  crops  of  satisfactory  product  can  be  ob- 
tained. -., 

But  the  end-mother-liquor,  if  of  sufficient  value,  can  be  purified 
by  various  means  according  to  its  nature,  and  its  contents  recoY= ; 
ered  or  utilized  in  one  way  or  another.  For  instance,  when~tfre 
mother-liquor  from  Rochelle  salt  has  been  concentrated  several 
times  it  finally  becomes  dark-colored  from  finely  divided  carj 
bon,  and  a  white  or  colorless  salt  can  then  no  longer  be  obtained 
from  it ;  but  if  the  end-mother-liquor  be  rendered  strongly-  acid 
by  the  addition  of  hydrochloric  acid  to  it,  the  valuable  tartrate 
radical  is  recovered  in  the  form  of  cream  of  tartar. 

164.  Creeping  salts.     In  the  evaporation  of  solutions  of  cer- 
tain ammonium  salts,  and  a  few  salts  of  potassium  and  sodium 
(as,  for  instance,  the  benzoates)  for  the  purpose  of  granulating 
or  crystallizing  these  salts,  it  happens  that  the  salt  is  deposited 
on  the  sides  of  the  evaporating-dish  above  the  level  of  the  liquid, 
and  that  the  solution  creeps  up  by  capillary  action  between  the 
particles  of  salt  and  the  crust  thus  formed  by  evaporation  of  this 
solution  extends  over  the  top  of  the   dish  and   on   its  outside 
unless  the  salt  is  scraped   down   from  time  to  time.     But  the 
"creeping"  may  be  prevented  by  slightly  greasing  the  dish. 

165.  The  crystals  may  be  collected  with  casseroles,  scoops, 
ladles,  spoons,  or  otherwise,  according  to  their  quantity.     Small 
crops  are  usually  loosened  from  the  crystallizer  and  poured  into  a 
funnel  with  the  mother-liquor.     When  very  small  quantities  are 
crystallized  the  mother-liquor  may  be  allowed  to  evaporate  to 
dryness. 


CRYSTALLIZATION    FROM    SOLUTIONS.  95 

166.  The  wet  crystals  must  be  washed  if  the  mother-liquor 
is  dirty  or  impure.  For  this  purpose  they  are  placed  in  a  per- 
forated funnel  or  draining-  cone,  and,  after  the  mother-liquor 
has  run  off,  the  mass  of  crystals  may  be  hastily  rinsed  with  a 
small  amount  of  cold  distilled  water.,  or  with  a  little  alcohol  if 
not  objectionable  on  chemical  grounds.  Crystals  washed  with 
alcohol  are  easily  dried. 

Before  washing  the  crystals  with  water,  it  is  necessary  to 
break  up  any  clumps. 

The  water  used  in  washing  the  crystals  usually  spoils  their 
appearance  somewhat  by  taking  off  the  sharp  edges.  To  avoid 
this  they  may  be  washed  with  a  pure  saturated  solution  of  the 
same  substance. 

c&ystals  formed  in  solutions  made  from  pure  substances,  of 
cojgfee  do  not  need  washing. 

*±87.     Wet  crystals  and  crystalline  products  are  drained  in  per- 
funnels,  or  draining  cones,  or  on  muslin  strainers.    When 
quantities  of  crystals  are  formed  in  dishes  or  beakers  these 
vessels  may  be  tilted  in  such  a  way  as  to 
allow  the  mother-liquor  or  wash-water 
to  run  off.     The  wet  crystals  or  mass 
should  be  allowed  to  stand  long  enough 
to  become  thoroughly  freed  from  liquid, 
so  that  they  are  nearly  or  quite  dry,  un- 
less greater  despatch  is  necessary. 
Fig.  90.  Position  of  dish  for       The  Buchner  funnel  (tig.  18)  and  the 

draining  of  crystals. 

centnfugator  (fig.  91)  are  also  used  in 
freeing  crystals  from  water. 

Small  quantities  of  wet  or  moist  crystals  may  be  drained  or 
even  dried  on  porous  tiles  or  on  pure  white  blotting  paper  or 
filter  paper.  But  handsome,  slender  crystals  should  not  be 
pressed  between  paper  or  cloth  if  they  are  so  frail  as  to  be  broken 
or  crushed  by  that  treatment. 

168.     The  drying  of  crystals  is  a  very  important  matter. 

Substances  which  are  permanent  in  the  air  and  not  affected  by 
moderate  heat  may  be  very  easily  dried  in  layers  about  15  to  20 
millimeters  thick  on  plates  of  glass.  Double  thick  window  glass 
is  suitable. 

The  product  should  be  frequently  stirred  or  turned  with  a  por- 
celain spatula  or  other  suitable  stirrer. 


96 


CRYSTALLIZATION    FROM    SOLUTIONS. 


Hydrous  crystals  should  be  dried  at  temperatures  not  above 
30°  to  40°. 

Efflorescent  and   deliquescent  hydrous   salts  are  liable  to  be 
partially  dissolved  in  their  own  water  if  dried  at  a  too  high  tem- 
perature, and  this  would  greatly  damage  if  not  ruin  the  product. 
Alcohol-washed  crystals  dry  readily. 

Anhydrous  crystals  may  in  most  cases  be  dried  at  100°  to  120°  ; 
but  if  this  is  not  convenient  they  may  be  exposed  a  longer  time 
and  dried  at  a  lower  temperature. 

When  crystalline  or  other  salts  are  dried  with  the  aid  of  heat, 
it  is  necessary  to  know  whether  or  not  they  are  in  any  way 
changed  or  injured  by  the  heat  to  which  they  are  exposed,  and 
the  temperature  must  be  regulated  accordingly. 

Sodium  bicarbonate  when  dried  with  the  aid  of  heat  is  liable 
to  give  off  CO2  as  well  as  water.  Ace- 
tates dried  with  or  without  the  aid  of 
heat  are  liable  to  lose  acetic  acid.  Lead 
acetate  in  very  small  crystals  should  be 
dried  in  an  atmosphere  of  acetic  acid 
vapor. 

Crystals  dried  by  exposure  to  the  air 
are  liable  to  be  of  dull  appearance. 

Crystals  may  be  quickly  dried  by  cen- 
trifugation.  When  draining  is  imprac- 
ticable, as  when  the  adhering  mother- 
liquor  is  dense  or  syrupy,  the  drying  is 
effected  in  rapidly  revolving  perforated 
drums.  Granulated  sugar  is  dried  in  that 
way.  The  small  centrifugal  machine 
figured  in  this  text  may  sometimes  be 
used  to  advantage  for  drying  efflorescent 
salts  and  other  products  difficult  to  dry 
in  the  usual  simple  way  (by  exposure  to  the  air). 

Desiccators  are  rarely  used  for  drying  inorganic  substances. 
They  are  glass  bells  placed  upon  plates  of  glass  over  vessels 
containing  fused  calcium  chloride,  calcium  oxide,  concentrated 
sulphuric  acid,  or  other  very  hygroscopic  substances  which  ab- 
sorb the  water  vapor  given  off  from  the  crystals  or  other  sub- 
stances placed  above,  or  beside  them.  See  fig.  53. 

169.     Before  being  bottled  the  product  must  be  perfectly  dry, 


Fig.  91.  A  centrifugator  for 
removing  mother  liquor 
and  water  from  crystals 
and  precipitates. 


CRYSTALLIZATION    FROM    SOLUTIONS.  Q? 

//  possible,  and  the  bottle  in  which  it  is  to  be  put  must  be  perfectly 
dry  and  warm.  After  the  bottle  is  filled  it  should  at  once  be 
tightly  closed. 

170.  Physical  precipitation.  The  separation  of  solids  from 
their  solutions  may  be  effected  by  the  addition  of  liquids  miscible 
with  the  solvent  but  in  which  the  substances  contained  in  the 
solutions  are  not  soluble. 

Many  water-soluble  salts  which  are  insoluble  in  alcohol  may 
thus  be  precipitated  or  separated  in  the  form  of  small  crystals 
by  the  addition  of  sufficient  alcohol  to  their  respective  water- 
solutions. 

Sometimes  this  method  of  obtaining  salts  in  a  granular  con- 
dition or  in  minute  crystals  is  also  at  the  same  time  an  effective 
method  of  purification  when  the  impurities  are  soluble  in  the 
precipitant,  as  in  the  preparation  of  precipitated  ferrous  sulphate. 

Substances  soluble  in  alcohol  but  insoluble  in  water  may  be 
precipitated  from  their  alcoholic  solutions  by  means  of  water. 

Physical  precipitation  usually  produces  a  crystalline  precipitate 
when  the  product  is  an  inorganic  salt.  When  ferrous  sulphate, 
copper  sulphate,  tartar  emetic,  and  certain  other  water-soluble 
salts  insoluble  in  alcohol  are  precipitated  by  adding  alcohol  to 
their  strong  water-solutions,  or  by  pouring  the  solutions  into 
alcohol,  the  crystalline  precipitates  thus  obtained  are  easily  and 
quickly  dried  because  wet  with  alcohol  instead  of  water. 


Vol. 


CHAPTER   XL 


DIALYSIS. 

171.  Dialysis  is  a  process  by  which  "crystalloids"  may  be  com- 
pletely eliminated  from  "colloids"  when  both  kinds  of  substances 
occur  together  in  water-solutions.  It  is  the  diffusion  of  crys- 
talloid matter '  in  aqueous  solution  through  a  suitable  organic 
septum.  The  septum  generally  used  is  parchment  paper.  This 
is  tied  tightly  over  a  circular  frame  of  glass,  porcelain,  hard  rub- 
ber, or  wood,  so  that  the  frame  forms  a  vessel  resembling  a  sieve 
of  which  the  parchment  paper  is  the  sieve  cloth  or  bottom.  This 
apparatus  is  called  a  dialyser,  and  when  it  is  used  the  solution 
which  is  to  be  subjected  to  dialysis  is  placed  in  the  dialyser  which 
is  suspended  in  a  large  vessel  containing 
water,  as  shown  in  the  cut. 

172.  Crystalloids  are  substances  which 
resemble  crystallizable  water-soluble  com- 
pounds in  that  they  pass  through  such 
septa  as  parchment  paper  when  in  a  state 
of  solution  in  water  and  placed  in  a  dialyser. 
All  water-soluble  crystallizable  salts  are 
crystalloids  ;  but  crystalloids  are  not  neces- 
sarily crystallizable. 

Colloids   (from  collum,  glue,  and  eidos, 
like)    are  water-soluble   substances    which, 

like  glue,  gelatin,  gum,  etc.,  are  unable  to  pass  through  the  dialy- 
ser in  the  manner  described. 

Crystalloids  and  colloids  can,  therefore,  be  separated  from  each 
other  by  dialysis. 

173.  Dialysis  is  employed  in  chemical  processes  to  separate 
inorganic  crystalloids  from  organic  colloids,  for  the  purification  of 
certain  chemical  products,  etc. 

Arsenical  compounds,  lead  salts,  poisonous  alkaloidal  salts,  etc., 
taken  into  the  stomach,  may  be  completely  dialysed  out  of  the 
mixture  of  the  total  contents  of  that  stomach,  and  then  easily 
separated  and  identified. 

98 


Fig.  92.  Dialyser. 


DIALYSIS.  99 

Salicylic  acid  may  be  freed  from  impurities  by  dialysis. 

The  preparation  called  "dialysed  iron"  is  a  water-solution  of  a 
compound  formed  by  saturating  a  dilute  solution  of  ferric  chloride 
with  ferric  hydroxide  and  then  removing  by  dialysis  whatever 
ferric  chloride  remains  unchanged,  together  with  the  ammonium 
salt  left  in  the  ferric  hydroxide  should  this  be  incompletely 
washed  (or  not  washed  at  all). 

The  liquid  passing  out  of  the  dialyser  is  called  the  diffusate. 

To  perform  dialysis  successfully  the  dialyser  should  not  be 
rilled,  but  should  contain  a  quantity  of  liquid  not  over  10  to  15 
millimeters  in  depth. 


CHAPTER  XII. 

PRECIPITATION. 

174.  Precipitation  is  the  formation  of  insoluble  solid  matter 
in  a  liquid. 

The  insoluble  solid  formed  is  called  a  precipitate. 

The  precipitate  may  be  absolutely  insoluble  in  the  liquid  in 
which  it  is  formed,  or  it  may  be  so  sparingly  soluble  as  to  be 
"practically  insoluble."  It  may  be  nearly  insoluble  in  that  liquid 
at  the  ordinary  room  temperature,  but  more  soluble  in  t,he  same 
liquid  at  a  higher  temperature,  and  may  be  very  soluble  in  other 
liquids. 
•  Precipitation  occurs  only  in  liquids. 

175.  It  is  important  that  distinction  be  made  between  physical 
precipitation  and  chemical  precipitation. 

Physical  precipitation  occurs  when  a  sufficiently  strong  solu-- 
tion  of  a  solid  substance  is  mixed  with  a  sufficient  proportion  of 
some  liquid  miscible  with  the  solvent  but  in  which  the  dissolved 
substance  is  insoluble.  The  dissolved  substance  is  then  more  or 
less  completely  thrown  out  of  its  solution,  re-assuming  the  solid 
state.  No  chemical  reaction  takes  place  in  physical  precipitation, 
for  all  the  substances  contained  in  the  liquid  before  and  after 
the  precipitation,  including  the  solid  substance  precipitated,  were 
already  present  or  added  and  no  new  substance  is  formed. 

Chemical  precipitation  results  from  the  formation  of  new  mole- 
cules in  a  liquid,  or  a  mixture  of  liquids,  one  or  more  of  the 
new  substances  being  insoluble  in  the  liquid  or  mixture.  Chemi- 
cal precipitation  is,  therefore,  always  caused  by  chemical  reac- 
tion, and  the  precipitate  is  in  all  cases  of  chemical  precipitation  an 
insoluble  product  of  that  reaction.  The  chemical  reactions  by 
which  precipitates  are  formed  may  or  may  not  be  complete  ac- 
cording to  the  proportions  of  the  reacting  factors  and  according 
to  other  circumstances  attending  the  precipitation. 

It  will  be  seen  from  the  foregoing  that  physical  precipitation  re- 
sults from  a  change  in  the  solvent  by  which  it  is  converted  into 
a  non-solvent,  while  the  substance  originally  held  in  solution,  and, 

100 


PRECIPITATION.  IOI 

therefore,  in  a  liquid  condition,  is  simply  separated  in  a  solid 
state;  chemical  precipitation,  on  the  contrary,  is  caused  not  by 
any  change  in  the  liquid  which  constitutes  the  solvent  of  the 
original  solution,  but  by  a  chemical  change  in  the  substances  dis- 
solved. 

176.  The  separation  of  solid  matter  from  a  solution  previously 
free  from  solid  particles  is  not  precipitation  if  the  solid  matter  is 
soluble  in  the  liquid  and  is  separated  for  want  of  a  sufficient  pro- 
portion of  the  solvent  to  retain  it  in  solution. 

The  crystallization  of  a  salt  from  its  solution  differs  from  pre- 
cipitation in  several  ways.  Crystallization  takes  place  more 
slowly,  whereas  precipitates  are  generally  formed  precipitately. 
Crystals  are  formed  in  saturated  solutions  by  a  reduction  of  the 
temperature  or  by  loss  of  a  portion  of  the  solvent  by  evaporation, 
and  they  grow  by  further  cooling  or  evaporation  of  the  solution 
in  which  they  wei  e  formed ;  but  precipitates  are  formed  in  dilute 
as  well  as  in  strong  solutions,  generally  without  reference  to  the. 
temperature  of  the  liquids  in  which  they  are  formed,  and  the 
particles  of  solid  matter  constituting  the  precipitate  do  not  in- 
crease in  size  unless  crystalline  and  contained  in  a  saturated 
solution  of  the  same  substance. 

Amorphous  solids  may,  also,  separate  from  saturated  solutions 
by  lowering  the  temperature  or  by  the  evaporation  of  the  solvent, 
and  depositions  of  amorphous  solids  from  their  solutions  are 
always  called  precipitation,  while  the  formation  of  crystals  in 
liquids  may  not  properly  be  called  precipitation  unless  the  crys- 
tals are  formed  as  the  result  of  chemical  reactions  and  formed 
precipitately.  The  slow  formation  of  precipitates  is  exceptional. 

177.  Chemical  precipitation  is  the  chief  subject  of  this  chapter, 
and  its  great  importance  may  be  recognized  from  the  fact  that 
nearly  all  insoluble  inorganic  solids  and  many  soluble  ones  are 
produced  by  metathesis  resulting  in  the  formation  of  one  sol- 
uble and  one  insoluble  product. 

178.  Precipitation  results   from  the  law,  that,   whenever,  in 
case  of  metathesis  between  two  soluble  salts  which  are  mixed 
with  each  other  in  a  state  of  solution,  an  insoluble  product  (or  a 
product  less  soluble  than  either  of  the  factors)  would  be  formed, 
then  that  metathesis  will  certainly  take  place  and  will  proceed  to 
completion. 

179.  The  materials  required  for  the  production  of  insoluble 


IO2  PRECIPITATION. 

chemical  compounds  by  precipitation  are,  with  rare  exceptions, 
soluble  compounds.  Hence  the  compounds  of  potassium,  so- 
dium (and  ammonium)  are  very  largely  employed  to  furnish  the 
negative  radicals  of  the  insoluble  inorganic  products,  and  the 
sulphates,  nitrates  and  chlorides  of  the  other  metals  are  the  most 
common  materials  furnishing  the  positive  radicals  (the  metals) 
toward  the  formation  of  the  same  products.  (See  Chapter  XIX, 
Vol.  I.)  Thus  the  factors  of  the  reactions  are  chiefly  salts. 
They  must,  of  course,  be  of  satisfactory  quality. 

180.  Proportions  of  the  factors.  While  the  relative  quantities 
to  be  taken  of  the  materials  are  always  computed  on  the  basis 
of  the  number  of  molecules  required  of  each  to  complete  the 
reaction  (as  shown  by  the  chemical  equation  representing  it), 
it  must  be  borne  in  mind  that  the  exact  proportions  thus  found, 
although  absolutely  correct  in  theory,  rarely  give  satisfactory 
results,  because  in  the  production  of  insoluble  compounds  by  pre- 
cipitation it  is  almost  invariably  necessary  that  the  factor  supply- 
ing the  positive  radical  of  the  insoluble  product  shall  be  com- 
pletely decomposed,  and  for  this  reason  the  other  factor  of  the 
reaction  must  be  used  in  excess  of  the  proportion  indicated  by 
theory. 

Thus,  when  an  insoluble  iron  compound  is  to  be  prepared  by 
precipitation  the  iron  salt  used  for  that  purpose  must  be  com- 
pletely decomposed ;  if  a  mercury  compound  is  to  be  made  all 
of  the  mercuric  chloride  used  must  be  consumed ;  if  a  lead  com- 
pound is  prepared  out  of  lead  nitrate  not  a  trace  of  the  lead  nitrate 
must  be  left  over.  Experience  has  shown  that  if  an  insoluble 
compound  of  any  given  metal,  when  it  is  being  formed  by  pre- 
cipitation, is  allowed  to  come  in  contact  with  a  soluble  com- 
pound of  the  same  metal  contained  in  the  liquid  in  which  the  reac- 
tion is  effected,  the  composition  of  the  product  sought  may  not  be 
normal.  Pure  mercuric  iodide  is  never  formed  when  solutions 
containing  the  exact  theoretical  proportions  of  mercuric  chloride 
and  potassium  iodide  are  mixed ;  pure  mercuric  oxide  is  not 
formed  when  the  exact  theoretical  proportions  of  mercuric 
chloride  and  sodium  hydroxide  are  mixed;  pure  normal  ferric 
hydroxide  is  not  obtained  when  ammonia  is  added  to  a  solution  of 
ferric  sulphate. 

An  excess  must,  therefore,  be  used  of  that  factor  which  sup- 


ITATION.  IO3 

plies  the  negative  radical  of  the  precipitate  in  order  that  every 
molecule  of  the  other  factor  may  be  decomposed. 

To  insure  that  a  pure  lead  iodide  is  obtained  from  lead  acetate 
and  potassium  iodide,  an  excess  of  the  potassium  iodide  is  neces- 
sary in  order  that  no  lead  acetate  may  be  left  undecomposed,  for 
if  lead  iodide  in  the  act  of  its  formation  as  a  precipitate  comes 
in  contact  with  lead  acetate  in  solution  the  precipitate  will  not 
consist  of  pure  lead  iodide  but  of  so-called  "oxy-iodide"  of  lead. 

How  much  of  an  excess  is  actually  necessary  it  is  difficult  to 
state.  Perhaps  from  three  to  five  per  cent  is  a  sufficient  addition 
to  the  quantity  theoretically  required ;  but  in  cases  where  experi- 
ence has  shown  that  the  tendency  toward  the  formation  of  meta- 
compounds,  "basic  compounds,"  double-salts,  and  other  abnor- 
mal or  undesired  products,  is  great,  an  excess  of  even  ten  per 
cent  above  the  quantity  called  for  according  to  the  chemical  equa- 
tion may  be  requisite.  A  considerable  excess  is  safer  than  a 
very  small  one,  and  no  disadvantage  can  attend  the  use  of  a  larger 
quantity  than  is  really  necessary  except  that  it  would  be  an  un- 
necessary waste.  The  practical  question  before  the  operator  is 
simply  which  of  the  two  evils  he  will  choose — a  slightly  increased 
cost  of  production  without  any  risk  of  spoiling  the  product,  or  the 
reduction  of  the  cost  of  production  to  a  minimum  coupled  with 
the  danger  of  obtaining  an  unsatisfactory  product.  In  this  con- 
nection it  is  well  to  take  into  consideration  the  fact  that  in  the 
production  of  inorganic  chemicals  the  necessary  labor  and  skill 
are  quite  generally  worth  much  more  than  the  cost  of  the  mate- 
rials. 

181.  The  solutions  used  for  making  precipitates  must  be  per- 
fectly clear.  Filtration  is  almost  invariably  necessary  to  insure 
this. 

It  may  be  said  that,  within  certain  limits,  dilute  solutions 
are  more  favorable  to  free  and  complete  chemical  interaction  than 
strong  solutions.  But  the  strength,  or  the  degree  of  concentration 
or  dilution,  which  ought  to  be  fixed  upon  in  each  case  must  be 
determined  by  several  circumstances.  In  some  cases  the  materials 
employed  may  not  be  sufficiently  freely  soluble  to  admit  of  the 
use  of  any  other  than  weak  solutions. 

Comparatively  dilute  solutions  should  always  be  made  of  any 
salts  the  complete  decomposition  of  which  is  to  be  insured ;  and 
stronger  solutions  should  be  made  of  any  alkalies  or  salts  which 


IO4  PRECIPITATION. 

are  to  be  present  in  excess  in  the  liquid  in  which  the  reaction 
takes  place.  Thus  when  ferric  hydroxide  is  made  from  solutions 
of  ferric  chloride  and  ammonium  hydroxide,  the  iron  solution 
should  be  weak  but  the  ammonia  less  dilute.  When  yellow  oxide 
of  mercury  is  made  the  solution  of  sodium  hydroxide  need  not 
be  very  diluted,  and,  in  fact,  ought  not  to  be  so,  but  the  solution  of 
mercuric  chloride  must  be  weak. 

Dilute  solutions,  as  a  rule,  make  light  or  bulky,  finely  divided 
precipitates,  while  strong  solutions  produce  heavier  or  denser, 
coarser,  precipitates. 

But  experience  is  the  best  guide.  Therefore,  unless  the  laborant 
has  had  sufficient  experience  of  -his  own,  he  should  be  guided  by 
that  of  others.  The  directions  given  in  reliable  laboratory  man- 
uals are  based  upon  the  experience  of  many  operators. 

The  temperature  of  the  solutions  is  also  a  matter  of  consider- 
able importance  in  many  precipitations.  Some  precipitates  are 
liable  to  be  decomposed  or  otherwise  injuriously  affected  by  heat 
and,  therefore,  require  to  be  made  from  cold  solutions.  Cold 
solutions  frequently  produce  more  bulky  and  finely  divided  pre- 
cipitates where  hot  solutions  make  denser  products. 

182.  The  order  of  mixing  the  solutions  is  often  one  of  the 
necessary  conditions  of  success. 

It  is  necessary  to  make  proper  distinction  between  the  two 
solutions  employed  for  the  production  of  precipitates  by  meta- 
thesis, and  the  only  technical  terms  I  find  in  use  are  the  words 
"precipitant"  and  "precipitand."  The  solutions  are  necessarily 
mixed  by  adding  one  to  the  other.  [The  suggestion  that  both 
solutions  be  simultaneously  poured  together  into  the  precipitation 
vessel  is  probably  not  of  any  value  in  a  single  instance.]  The 
solution  first  put  into  the  precipitation  vessel  was  called  the  "pre- 
cipitand ;"  and  the  other  solution,  poured  into  the  first  one,  was 
called  the  "precipitant."  Many  have  discarded  or  refused  to 
adopt  the  term  precipitand  because  it  is  scarcely  possible  to  pro- 
nounce the  two  words  so  distinctly  that  one  is  not  mistaken  for 
the  other.  I  shall,  therefore,  use  the  expression  primal  solution 
in  this  book,  meaning  thereby  the  solution  which  is  put  in  the 
precipitation  vessel  first;  and  will  retain  the  term  precipitant  to 
designate  the  solution  which  is  to  be  added  to  the  primal  solution. 

But — which  of  the  two  solutions  shall  we  pour  into  the  jar 
nrst?  Let  us  consider  an  example.  The  so-called  "ammoniated 


PRECIPITATION.  IO5 

mercury"  of  the  pharmacopoeias  is  an  insoluble  compound  made 
by  mixing  a  solution  of  mercuric  chloride  and  a  solution  of  am- 
monium hydroxide  (ammonia  water).  Now,  if  we  put  the  solu- 
tion of  mercuric  chloride  into  the  jar  first  and  then  add  the  am- 
monia water,  the  solution  of  chloride  of  mercury  will  be  our 
primal  solution  and  the  ammonia  water  will  be  our  precipitant; 
but  if  we  put  the  ammonia  into  the  jar  first  and  then  pour  the 
mercury  solution  into  the  ammonia,  our  primal  solution  will  be 
the  solution  of  ammonium  hydroxide  and  the  solution  of  mercuric 
chloride  becomes  the  precipitant.  Will  it  make  any  difference 
what  course  we  pursue?  Decidedly.  If  we  use  the  solution  of 
mercuric  chloride  as  the  primal  solution,  and  ammonia  water  as 
the  precipitant,  the  precipitate  produced  will  be  a  compound  said 
to  consist  of  mercuric  chloramide  and  mercuric  chloride,  and 
usually  represented  by  the  formula  NH2(HgCl)2Cl ;  but  if  we 
use  the  ammonia  as  our  primal  solution  and  the  solution  of  mer- 
curic chloride  as  the  precipitant,  then  the  precipitate  produced 


will  be  pure  mercuric  chloramide,  Hg 

> 


Cl 


[The  NH2(HgCl)2Cl  is  said  to  be  ClHg—  N— HgCl  in  which 

H     H 

the  nitrogen  is  a  pentad  with  a  polarity-value  of  — 3,  the  only 
positive  nitrogen  bond  being  that  which  holds  the  one  chlorine 
atom  in  direct  combination.] 

If  the  student  will  now  refer  again  to  paragraph  180  he  will 
understand  that  the  primal  solution  must  be  the  solution  of  that 
factor  which  contributes  the  negative  radical  toward  the  forma- 
tion of  the  precipitate,  and  that  the  other  factor — the  one  con- 
tributing the  positive  radical  of  the  precipitate — must  be  made 
the  precipitant. 

As  the  scope  of  this  book  is  limited  to  the  inorganic  chemical 
compounds,  and  as  nearly  all  the  insoluble  inorganic  compounds 
made  by  precipitation  are  metallic  compounds,  we  can  simplify 
the  rule  just  given  as  follows:  An  insoluble  metallic  rnmpound 


IO6  PRECIPITATION. 

should  not  be  precipitated  in  a  primal  solution  containing  a  com- 
pound of  the  same  metal  that  enters  into  the  composition  of  the 
precipitate. 

A  precipitated  mecury  compound  should  not  be  produced  in  a 
solution  of  a  mercury  salt;  do  not  make  an  insoluble  iron  com- 
pound in  a  liquid  containing  a  soluble  iron  salt ;  do  not  let  an  insol- 
uble lead  compound  be  formed  in  a  solution  or  mixture  containing 
a  lead  salt ;  a  precipitated  copper  compound  should  not,  in  the  act 
of  its  formation,  be  allowed  to  come  in  contact  with  a  copper  solu- 
tion ;  do  not  let  an  insoluble  zinc  compound  lie  in  a  solution  of  a 
zinc  salt,  and  do  not  make  it  in  such  a  solution. 

If  ammonia  water  be  added  to  a  solution  of  ferric  sulphate  the 
reaction  will  be  as  follows: 

Fe2  ( SO4)  8+6H4NOH=2OFeOH+3  ( H4N  )  2SO4+2H2O. 

But  if  a  solution  of  ferric  sulphate  be  added  to  ammonia  water 
the  result  is: 

Fe2(S04)3+6H4NOH=2Fe(OH)3+3(H4N)2S04. 

It  is  clear  that  if  ammonia  water  is  gradually  added  to  a  solu- 
tion of  ferric  sulphate,  the  ferric  sulphate  will,  at  least  at  the  be- 
ginning, be  present  in  excess;  but  if  the  order  of  mixing  the 
liquids  be  reversed,  the  ammonia  water  will  be  in  excess.  With 
the  ammonia  present  in  excess  it  is  impossible  to  obtain  any  other 
products  than  Fe(OH)3  and  (H4N)2SO4,  for  the  Fe(OH)3  is 
insoluble  in  and  unaffected  by  the  ammonia  water  and  the  am- 
monium sulphate ;  all  of  the  ferric  sulphate  is  decomposed  as  fast 
as  it  is  added,  and  there  is  accordingly  no  ferric  salt  present  in 
the  solution  at  any  time.  But  when  the  solution  of  ferric  sulphate 
is  used  as  the  primal  solution  and  the  ammonia  water  as  the  pre- 
cipitant the  ferric  hydroxide,  Fe(OH)3,  first  formed  redissolves 
in  the  solution  of  ferric  sulphate : 

2Fe(OH)3+5Fe2(S04)3=3Fe40(S04)5+3H20. 

Subsequently,  when  more  ammonia  is  added,  the  "basic  ferric 
sulphate"  is  decomposed: 


PRECIPITATION.  IO? 

Fe4O(SO4)5+ioH4NOH= 

4OFeOH+5(H4N)2S04+3H20. 

Assuming  that  the  proportions  of  the  factors  are  correct,  we 
know  that,  when  one  liquid  is  added  to  the  other,  the  precipitant 
is  completely  decomposed  as  fast  as  added,  and  the  primal  solution 
remains  in  excess  from  beginning  to  end,  provided  other  condi- 
tions are  favorable. 

183.  To  insure  complete  decomposition  of  the  precipitant  as 
fast  as  it  is  added  to  the  primal  solution,  it  is  necessary  to  observe 
the  following  precautions : 

a.  The  precipitant  should  be  a  rather  dilute  solution,  while  the 
primal  solution  should  be  less  diluted  (but  not  concentrated). 

b.  The  precipitant  should  be  added  slowly,  or  gradually,  and 
this  is  best  accomplished   (when  great  caution  is  necessary)  by 
running  it  into  the  primal  solution  through  a  syphon  of  small 
diameter.    Or  the  precipitant  may  be  added  in  small  portions,  one 
portion  at  a  time. 

c.  The  primal  solution  should  be  well  stirred,  as  the  precipitant 
is  added,  and  brisk  stirring  of  the  mixture  should  be  continued 
without  interruption  until  all  of  the  precipitant  has  been  used. 

It  may  be  readily  seen  that  if  the  precipitant  be  added  too 
rapidly,  in  rather  large  quantities,  and  without  stirring,  some  of 
the  newly  formed  precipitate  may  come  in  contact  with  portions 
of  the  undecomposed  precipitant,  which  is  the  danger  to  be  par- 
ticularly guarded  against. 

184.  When  very  concentrated  solutions  are  used  the  reaction 
is  liable  to  be  incomplete,  especially  if  the  precipitate  is  bulky. 

The  precipitation  is  generally  more  complete  when  hot  liquids 
are  used ;  but  hot  solutions  should  not  be  employed  unless  it  is 
certain  that  the  precipitate  will  not  be  injuriously  altered  by  the 
higher  temperature. 

185.  Occasionally  the  proportions  of  the  factors  of  the  reac- 
tion can    not  be  fixed    beforehand    in    accordance    with    their 
molecular  weights.    This  happens  when  the  quantity  of  the  com- 
pound contained  in  the  primal  solution  is  unknown.     The  precip- 
itant is  then  to  be  added  cautiously,  a  small  portion  at  a  time, 
until  it  ceases  to  cause  further  precipitation.     To  guard  against 
adding  an  excess  of  the  precipitant  in  such  cases  it  is  best  to  test 


IO8  PRECIPITATION. 

the  liquid  from  time  to  time  by  filtering  off  a  test  sample  and 
testing  that  with  a  drop  or  more  of  the  precipitant.  Complete 
and  even  precipitation  may  thus  be  accomplished  if  admissible; 
but  it  is  generally  best  to  stop  the  further  addition  of  precipitant 
before  quite  all  of  the  other  factor  of  the  reaction  (that  contained 
in  the  primal  solution)  has  been  decomposed,  and  in  no  case 
should  an  excess  of  the  precipitant  be  used  unless  requisite  for 
some  special  reason  or  known  to  be  proper. 

186.  The  precipitate.  Precipitates  vary  greatly  in  their  physi- 
cal properties.  They  may  be  crystalline  or  amorphous,  heavy  or 
light,  dense  or  bulky,  coarse  or  fine ;  they  may  be  granular,  or 
curdy,  or  flocculent,  or  gelatinous.  A  very  bulky,  finely  divided, 
amorphous,  almost  pasty  or  gelatinous  precipitate  tenaciously 
retaining  much  water,  is  called  a  magma. 

We  have  said  that  hot  and  strong  solutions  are  likely  to  produce 
denser,  heavier  and  coarser  precipitates,  whereas  cold  and  dilute 
solutions  tend  to  produce  bulkier,  lighter  and  finer  precipitates. 
But  the  denser  precipitates  formed  in  hot  liquids  generally  be- 
come bulkier  if  allowed  to  remain  in  the  liquids  long  after  they 
have  become  cold,  and  bulky  precipitates  become  denser  if  left 
a  long  time  in  the  liquids  in  which  they  are  formed.  Precipitates 
should,  therefore,  be  collected  and  washed  as  expeditiously  as 
practicable  if  it  is  desired  to  prevent  such  changes.  The  hydrox- 
ides, carbonates  and  phosphates  of  calcium,  magnesium,  and  iron, 
and  aluminum  hydroxide,  when  precipitated  in  the  cold,  are  so 
bulky  and  finely  divided  as  to  be  nearly  gelatinous,  and  they  are, 
therefore,  precipitated  from  hot  solutions,  instead ;  but  if  they  are 
allowed  to  remain  in  the  liquid  until  it  becomes  cold,  and  washed 
with  cold  water,  the  object  of  the  use  of  hot  solutions  is  at  least 
partially  defeated. 

Precipitates  which  contain  water,  or  from  which  water  may  be 
split  off  by  rearrangements  of  the  interatomic  linking,  vary  in 
composition  according  to  the  temperature  of  the  liquids  in  which 
they  are  formed.  This  variableness  may  be  observed  in  mag- 
nesium carbonate,  the  carbonates  of  zinc  and  of  lead,  ferric  hy- 
droxide, and  severarother  compounds.  Precipitates  made  and 
washed  in  hot  liquids  sustain  a  loss  of  water;  those  made  and 
washed  in  cold  liquids  do  not.  On  the  other  hand,  some  pre- 
cipitates take  up  water  when  long  exposed  to  its  action  at  the 
ordinary  room  temperature,  or  they  may  undergo  other  changes. 


PRECIPITATION. 


109 


Bismuth  stibnitrate,  when  allowed  to  remain  wet  too  long,  or 
when  it  lies  in  a  large  quantity  of  water,  becomes  denser,  coarser 
and  "more  basic"  (that  is,  its  composition  changes  so  that  the 
proportion  of  metal  in  it  seems  to  be  increased,  probably  by  the 
splitting  off  of  water  and  acid). 

Whenever  the  precipitate  is  to  any  extent  soluble  in  the  liquid 
in  which  it  is  formed  and  is  at  the  same  time  capable  of  assum- 
ing a  crystalline  form,  the  use  of  hot  liquids  may  cause  the  prod- 
uct to  be  coarser  and  more  distinctly  crystalline.  This  is  some- 
times desirable  as  a  means  of  improving  the  appearance  of  the 
product.  In  such  a  case  it  is  necessary  to  let  the  liquid  cool 
gradually,  but  thoroughly,  to  render  the  crystals  larger,  and  to 
reduce  to  a  minimum  the  amount  lost  by  being  retained  in  the 
liquid. 

187.  The  inorganic  compounds  most  frequently  made  by  pre- 
cipitation are  the  oxides,  hydroxides,  sulphides,  carbonates,  oxal- 
ates  and  phosphates  of  the  heavy  metals,  the  carbonates  and 
phosphates  of  calcium,  strontium,  barium  and  magnesium,  the 
halides  of  silver,  lead  iodide,  mercurous  chloride  and  iodide,  and 
mercuric  iodide. 

188.  Precipitation  vessels.     The  best  precipitation  vessels  for 


Fig.  93.  Precipitation  jar. 


Fig.  94.    Tubulated  decantation  vessel. 


large  operations  are  stoneware  pats,  which  may  conveniently  be 
of  from  5  liters  to  250  liters  capacity.  When  larger  vessels  are 
required  wooden  tanks  are  often  suitable.  Tubs  and  barrels  are 
also  employed. 


no 


PRECIPITATION. 


Special  so-called  "precipitating  jars"  of  glass,  porcelain,  or 
other  earthenware,  are  sometimes  used.  They  are  tall,  round 
vessels,  wider  at  the  bottom  than  at  the  top,  as  shown  in  the  cut. 

Some  precipitation  and  decantation  vessels  are  tubulated,  or 
provided  with  spigots  or  taps  at  various  heights,  as  shown  in  fig. 
94  to  serve  as  outlets  for  the  -  removal  of  the  supernatant  liquid 
whenever  the  precipitate  has  subsided  sufficiently. 


Fig.  95.  Beaker  with  lip.      Fig.  96.  Beaker    without    lip.       Fig.  97.  Precipitation 


But  any  well  glazed,  acid-proof  jars,  or  porcelain  or  glass  ves- 
sels may  be  used,  and  for  quite  small  quantities  the  ordinary 
Erlenmeyer  flasks,  beakers,  and  wide-mouth  bottles. 

189.  The  liquid  in  which  the  precipitate  is  formed,  obtained 
by  mixing  the  two  solutions  (the  precipitant  and  the  primal  solu- 
tion)  contains  the  bye-product  dissolved  in  it.     It  is  called  the 
mother-liquor,  the  same  technical  term  being  used  to  designate 
this  liquid  as  is  given  to  the  liquid  from  which  the  crystals  are 
deposited  in  the  process  of  crystallization.     If  the  precipitate  is 
heavy  enough  to  sink  down  to  the  bottom  of  the  precipitation 
vessel,  or  at  least  to  descend  below  the  surface  of  the  mother- 
liquor,  then  the  clear  or  nearly  clear  liquid  standing  above  the 
precipitate  is  called  the  supernatant  liquid. 

It  is  in  some  cases  important  to  remove  the  precipitate  from  the 
mother-liquor  or  supernatant  liquid  as  quickly  as  practicable, 
lest  the  product  be  unfavora-bly  affected  by  too  long  contact 
with  it. 

190.  Removal  of  the  mother-liquor  or    supernatant  liquid  is 
necessary  before  the  precipitate  can  be  effectively  washed. 


PRECIPITATION.  1 1 1 

Should  the  bye-product  contained  in  that  liquid  be  of  sufficient 
value  to  warrant  its  recovery  it  is,  of  course,  desirable  to  collect 
the  mother-liquor  with  as  little  loss  as  possible.  After  filtration 
the  solution  may  then  be  concentrated  by  evaporation  and  the 
bye-product  crystallized  out.  But  owing  to  the  necessity  of  em- 
ploying an  excess  of  one  of  the  factors  of  the  reaction  the  bye- 
product  is  rarely  pure,  and  must  b,e  purified  before  it  can  be 
utilized.  Should  this  be  the  case  the  mother-liquor  may  be  boiled 
down  to  concentrate  it  before  filtration,  and  the  filtrate,  or  the 
residue  obtained  upon  its  evaporation,  purified  by  whatever 
method  may  be  applicable  in  each  case.  Salts  recovered  from 
mother-liquors  after  precipitations  may  often  be  purified  by  re- 
peated recrystallizations.  When  the  bye-product  is  to  be  re- 
covered it  is  advantageous,  if  in  other  respects  unobjectionable, 
to  employ  strong  solutions  in  performing  the  precipitation,  for 
the  mother-liquor  will  then  be  less  diluted  and  less  concentration 
by  evaporation  will  be  required. 

If  the  bye-product  is  not  to  be  recovered  it  is  nevertheless  de- 
sirable to  separate  the  mother-liquor  from  the  precipitate  as  far 
as  possible  before  proceeding  with  the  washing-process,  because 
the  object  of  washing  the  precipitate  is  the  complete  removal  of 
all  of  the  soluble  matter  and  this  is  more  speedily  effected  by  first 
getting  rid  of  as  much  as  possible  of  the  mother-liquor  than  by 
removing  only  a  portion  of  it  and  diluting  the  remainder. 

Supernatant  liquids,  whether  mother-liquor  or  washings,  are 
removed  from  the  precipitate  by  decantation,  either  by  tilting  the 
precipitation  vessel  or  with  the  aid  of  the  tubulures  or  spigots  if 
a  tubulated  vessel  is  used,  or  with  a  syphon.  The  decantation  of 
liquids  and  the  utility  of  the  guiding  rod  and  greased  rim  have 
been  sufficiently  discussed  in  Chapter  VI.  The  preparation, 
riggmg  and  use  of  cloth  strainers,  and  the  use  of  presses  for  the 
separation  of  liquids  from  bulky  precipitates  are  also  described  in 
the  same  chapter. 

191.  The  washing.  After  the  mother-liquor  has  been  separ- 
ated from  the  precipitate  as  far  as  practicable,  the  soluble  matter 
of  which  a  considerable  quantity  still  remains  adhering  to  and 
contaminating  the  product  must  be  washed  out.  As  the  precip- 
itation itself  is  generally  performed  with  aqueous  solutions  and 
thje  bye-product  is  water-soluble,  the  washing  is  effected  with 
water. 


112  PRECIPITATION. 

The  water  used  for  this  purpose  may  be  either  hot  or  cold  ac- 
cording to  the  requirements  of  each  case.  When  hot  zvater  must 
or  can  be  used,  it  is  more  effective  in  removing  the  soluble  matter, 
so  that  a  smaller  quantity  of  hot  water  will  do  as  much  work  as  a 
larger  quantity  of  cold  water  and  do  it  more  quickly.  Another 
advantage  gained  when  hot  water  can  be  safely  used  is  that  it 
renders  the  subsidence  of  the  precipitate  easier  by  making  the 
liquid  lighter,  and  (in  some  cases)  the  precipitate  more  dense. 

192.  Rapid  washing  is  very  desirable  because  prolonged  con- 
tact with  water  frequently  causes  the  precipitate  to  contract  when 
this  is  not  desired,  or  it  may  have  the  opposite  effect  when  the 
precipitate  was  produced  from  hot  liquids. 

193.  Heavy  precipitates  are  the  easiest  to  wash.    They  subside 
rapidly   and   compactly   in  the  precipitation   vessel   so   that  the 
mother-liquor   can  be  almost   completely   removed.      The   wash 
water  is  then  added  and  the  precipitate  thoroughly  mixed  with  it 
by  vigorous  shaking  or  stirring;  the  first  "washings"  must  then 
be  thoroughly  removed  before  a  second  portion  of  water  is  added, 
the  shaking  or  stirring  repeated,  and  the  second  washings  also 
separated  before  a  third  portion  of  water  is  added.     By  repeating 
the  "affusion  and  decantation"  of  water  several  times  the  washing 
will  be  readily  finished. 

194.  Light  precipitates  and  magmas  are  not  so  easily  washed 
because  they  do  not  settle  down  to  the  bottom  of  the  precipitation 
vessel  either  rapidly  or  compactly.    Should  the  precipitate  remain 
suspended  in  the  mother-liquor  on  account  of  the  too  great  den- 
sity of  that  liquor  the  difficulty  may  sometimes  be  remedied  by 
dilution  (with  hot  water  if  admissible),  or  by  warming  the  mix- 
ture.    If  this  method  should  be  inadequate  or  inadmissible,  the 
thick  mixture  may  be  turned  into  a  muslin  strainer  and  allowed 
to  drain.    The  muslin  strainer  should  first  be  dipped  in  hot  water 
and  wrung  out  before  it  is  placed  on  the  frame  and  bagged  to 
receive  the  precipitate  or  magma.    Should  the  liquid  which  passes 
be  turbid  it  must  be  returned  until  it  runs  clear.    When  all  of  the 
liquid  has  passed  through  the  straining  cloth,  the  pasty  magma 
on  the  cloth  is  returned  to  the  cleaned  precipitation  vessel  (or  to 
any  other  suitable  pot)  and  there  thoroughly  mixed  with  water, 
after  which  the  mixture  is  turned  into  the  muslin  strainer  again 
and  the  washings  allowed  to  pass  through.    These  operations  are 


PRECIPITATION. 


then  repeated  as  many  times  as  may  be  necessary  to  complete  the 
washing. 

195.  When  small  quantities  are  treated  it  may  be  best  to  per- 
form the  washing  on  a  paper  filter.     A  plain  filter  (one  with  as 
few  folds  as  possible)  must  be  used  for  this  purpose.     A  folded 
paper  filter  can  be  made  to  fit  a  funnel  of  any  angle  by  making 
the  second  fold  either  larger  or  smaller  than  a  right  angle  to  the 
first  fold  of  the  paper,  according  to  whether  the  folded  filter  is 
too  wide  or  too  narrow  at  the  top  when  placed  in  the  funnel.     It 
is  best  to  make  the  angle  of  the  paper  filter  slightly  more  obtuse 
than  that  of  the  funnel.     Wetting  the  filter  promotes  clear  and 
rapid  filtration,  because  it  causes  the  paper  pulp  to  swell  so  that 
the  pores  of  the  paper  close  sufficiently  not  to  let  solid  particles 
pass  through,  whereas  if  a  fine  precipitate  is  allowed  to  get  into  the 
pores  before  the  paper  is  wetted  the  fibres  may  afterwards  swell 
so  as  to  close  the  pores  altogether  or  to  such  an  extent  that  no 
liquid  will  pass.    The  water  should  be  added  in  portions  and  each 
portion  allowed  to  pass  through  the  precipitate  and  out  of  the 
filter  before  another  portion  of  water  is  added. 

196.  In  washing  precipitates  on  paper  filters  the  "spritz  bottle" 
is  useful  for  the  purpose  of 

directing  a  stream  of  water 
on  the  filter  at  the  top  and 
all  around  so  as  to  wash 
down  the  precipitate  into 
the  throat  of  the  funnel 
where  it  can  be  more  easily 
covered  with  each  portion 
of  wash-water  added. 

197.  The  washing  may 
be    known    to    have    been 
completed  when  the  wash- 
water    no   longer   removes 
any   more   soluble   matter. 
The  presence  of  any  con- 
siderable quantity  of  the  soluble  bye-product  in  the  washings 
usually    makes   itself   known    by   the    taste,    which    is    in   most 
cases  saltish.     The  washing-process  is  continued  only  until  the 
washings  are  tasteless  whenever  circumstances  render  this  suf- 
ficient.    But   when    the   precipitate    is    to    be    a   pure    finished 

Vol.  II— 8 


Fig.  98.  Spritz-bottle. 


1 14  PRECIPITATION. 

product  it  is  necessary  to  use  chemical  reagents  to  determine  the 
completion  of  the  washing  from  the  entire  absence  of  the  soluble 
substances  in  the  end  washings.  The  soluble  substance  contained 
in  the  mother-liquor  and  washings  is  known  from  the  materials 
employed  and  the  reaction  which  occurs  between  them,  and  the 
reagent  required  is,  therefore,  also  known.  As  the  materials 
most  generally  used  are  sulphates  and  chlorides  the  reagents  for 
the  identification  of  these  compounds  are  much  in  demand  for 
testing  washings  in  the  preparation  of  precipitated  products. 
Thus  the  test  solutions  of  barium  nitrate  or  chloride,  and  silver 
nitrate,  are  the  most  common  reagents. 

198.  After  completing  the  washing-process  the  next  step  is 
usually  that  of  letting  the  precipitate  drain  preparatory  to  drying 
it.    The  draining  process  may  be  effected  on  a  cloth  strainer  or 
on  a  paper  filter,  according  to  the  quantity.    The  wet  precipitate 
is  allowed  to  lie  undisturbed  on  the  cloth  or  filter  until  no  more 
liquid  passes ;  the  dropping  sometimes  ceases  while  the  precipi- 
tate still  retains  much  water  and  in  such  cases  it  is  worth  while 
to  give  the  strainer  frame  or  funnel  a  gentle  tap,  which  often  has 
the  effect  of  causing  some  more  water  to  run  off. 

The  centrifugal  machine  may  sometimes  be  advantageously  em- 
ployed to  throw  off  moisture  from  wet  precipitates  as  well  as  from 
wet  crystals. 

199.  The  removal  of  drained  or  dried  precipitates  from  strain- 
ing cloths  and  filters  must  be  effected  with  sufficient  care.    If  the 
precipitate  has  been  thoroughly  drained  it  generally  comes  off 
very  easily,  and  if  allowed  to  dry  completely  on  the  cloth  or  paper 
it  often  comes  off  still  more  readily;  but  large  bodies  or  thick 
layers  of  magma  dry  too  slowly  and  are,  therefore,  generally 
spread  out  on  glass  plates  or  on  tiles  or  stoneware  dishes  to  dry. 

When  precipitates  have  been  drained  on  a  cloth  strainer  as 
far  as  practicable  they  may  be  loosened  or  if  necessary  scraped  off 
and  transferred  to  the  plates  on  which  they  are  to  be  dried,  or  to 
dry  cloths  placed  on  frames. 

To  remove  precipitates  from  paper  filters  the  paper  must  be 
carefully  unfolded  so  that  it  may  not  be  torn,  and  if  the  precip- 
itate adheres  to  the  paper,  rendering  it  necessary  to  scrape  it  off, 
this  must  be  done  cautiously  in  order  to  avoid  getting  fragments 
or  fibers  of  the  paper  mixed  with  the  product.  In  unfolding  the 
paper  filter  to  remove  the  precipitate  it  is  well  to  first  place  it  upon 


PRECIPITATION.  1 15 

a  clean  cloth  or  sheet  of  paper,  or  in  a  dish,  or  on  a  glass  plate. 

200.  The  drying  of  precipitates  is  occasionally  difficult.     All 
products  of  this  kind  must  be  thoroughly  dried.    The  drying  may 
frequently  be  effected  on  hot  plates,  or  on  frames  or  plates  in  a 
drying  room  or  drying  closet.     But  some  precipitates  either  do 
not  withstand  exposure  to  heat  or  dry  into  hard,  tough  cakes  that 
can  not  be  easily  reduced  to  soft,  fine  powder.    Many  precipitates 
form  soft,  friable,  light  masses  when  dried  at  the  ordinary  tem- 
terature,  and  this  is  a  great  advantage  because  the  cakes  or  lumps 
so  obtained  can  easily  be  gently  rubbed  through  a  fine  sieve  cloth 
to  form  soft,  fine,  bulky  products. 

Small  amounts  of  moist  or  wet  precipitates  which  can  not  be 
dried  in  the  ordinary  way  without  difficulty  or  much  delay  may 
be  spread  out  in  thin  layers  on  clean,  new,  porous,  unglazed  stone- 
ware dishes,  tiles  or  bricks,  which  may  in  many  instances  be  used 
warm  or  even  hot.  Common  flower  pot  dishes  are  often  used  to 
advantage.  But  porous  dishes,  tiles  and  bricks  can,  of  course, 
not  be  used  more  than  once. 

Precipitates  which  are  known  to  be  sensitive  and  liable  to  be 
injured  by  exposure  to  air  should  be  dried  as  quickly  as  practi- 
cable, and  those  that  are  injured  by  light  must  be  dried  in  a  dark 
place.  All  of  them  must  be  well  protected  against  dust  and  dirt ; 
they  may  be  loosely  covered  with  thin  muslin  or  white  filter 
paper. 

201.  Pulverization    of    precipitates.     Some    precipitates    are 
micro-crystalline  or  granular  and  form  coarse  or  moderately  fine 
powders  when  dry  without  requiring  any  pulverization.    But  pre- 
cipitates which  dry  in  hard  cakes  or  lumps  must  be  reduced  to 
very  fine  powder  by  sifting,  or  by  trituration  or  grinding  followed 
by  sifting.    The  finer  and  softer  the  powder  is  the  better,  unless 
it  be  of  perfectly  uniform  micro-crystalline  structure.     But  soft, 
friable  lumps  are  unobjectionable  in  several  cases,  according  to 
circumstances. 

202.  We  have  already  referred  incidentally  to  the  fact  that 
soluble  salts  may  also  be  prepared  by  metathesis  accompanied  by 
precipitation,  the  precipitate  being  the  bye-product.     It  is  neces- 
sary in  all  such  cases  to  carefully  guard  against  contamination  of 
the  soluble  product  by  the  presence  of  an  undue  excess  of  one 
of  the  substances  used  as  materials,  and  it  may  not  infrequently 
be  found  advantageous  to  employ  the  exact  proportions  required 


U6  PRECIPITATION. 

of  the  factors  according  to  the  chemical  equation  representing 
the  reaction  instead  of  using  an  excess  of  one  of  them,  or  it  may 
even  be  best  to  use  an  excess  of  that  factor  which  contributes  the 
positive  radical  toward  the  formation  of  the  insoluble  bye-product, 
and  then  also  to  mix  the. solutions  in  such  order  as  to  insure  the 
preponderance  of  the  right  one  of  the  factors  throughout  the 
chemical  interaction.  It  is  evident  that  in  all  these  cases  our  first 
concern  is  not  the  composition  of  the  precipitate  but  the  purity 
of  the  soluble  product. 

This  method  of  preparing  soluble  inorganic  salts  is  not  gener- 
ally employed  when  quite  pure  products  are  desired,  because  it 
does  not  generally  lead  to  satisfactory  results.  The  soluble  salts 
recovered  from  the  mother-liquors  of  precipitations  usually  re- 
quire purification  by  repeated  recrystallization  or  by  other  means 
to  render  them  fit  for  use. 

203.  Alcoholic  solutions,  and  solutions  made  with  glycerin, 
acetic  acid,  and  other  solvents,  instead  of  water-solutions,  are 
also  employed  in  the  production  of  precipitated  chemicals. 

Alcohol  and  other  liquids  may  also  be  used  instead  of  water  for 
washing  the  precipitates  in  special  cases  where  circumstances  re- 
quire it. 

204.  The  precipitant  may  sometimes  be  a  solid  or  a  gas  instead 
of  a  liquid  or  a  solution.     Calcium  carbonate  placed  in  a  solution 
of  bromide  of  iron  precipitates  the  iron  and  leaves  calcium  bro- 
mide in  the  solution.     Carbon  dioxide  precipitates  calcium  car- 
bonate from  solutions  containing  calcium  hydroxide,  and  barium 
carbonate  from  solutions  containing  barium  hydroxide.     Hydro- 
gen sulphide  is  often  conducted  into  solutions  containing  com- 
pounds of  arsenic  or  of  other  metals  for  the  purpose  of  removing 
the  metals  in  the  form  of  insoluble  sulphides. 

205.  The  purification  of  commercial  chemicals  is  frequently 
effected  by  precipitating  the  objectionable  impurities  from  their 
solutions.    Iron  may  be  thus  removed  from  solutions  of  zinc  salts, 
the  precipitant  used  being  zinc  oxide  or  zinc  carbonate,  and  iron 
is  removed  from  ammonium  chloride  by  adding  ammonia  to  the 
solution  of  the  chloride. 


CHAPTER   XIII. 

CHEMICAL    SOLUTION.       WET    OXIDATION.       WET    GAS    OPERATIONS. 

206.  Water-soluble  salts  and  some  other  water-soluble  inor- 
ganic solids  are  generally  produced  by  chemical   solution,  the 
product  being,  after  the  reaction,  recovered  from  the  solution  by 
crystallization  or  otherwise. 

The  most  common  chemical  solvents  are  the  acids ;  solutions 
of  the  alkalies  are  occasionally  employed,  and  even  solutions  of 
certain  salts. 

Metals,  or  their  oxides,  hydroxides  or  carbonates  are  dissolved 
in  hydrochloric  acid  to  produce  chlorides,  in  nitric  acid  to  make 
nitrates,  in  sulphuric  acid  to  make  sulphates,  in  acetic  acid  to  pro- 
duce the  acetates,  and  so  on.  This  method  is  practicable  whenever 
the  products  consist  of  a  water-soluble  salt  and  water,  or  a  water- 
soluble  salt  and  a  gas,  or  both  water  and  gas  together  with  the 
salt.  The  bye-products,  then,  are  generally  water,  hydrogen, 
carbon  dioxide,  sulphur  dioxide,  nitrogen  oxides,  according  to 
the  materials  employed. 

The  reactions  involved  in  processes  of  chemical  solution  are 
sometimes  substitution,  in  other  cases  metathesis,  and,  when  metals 
are  dissolved,  the  reactions  involve  oxidation  and  reduction. 

207.  When  acids  are  the  solvents  the  reactions  are  substitu- 
tion reactions  if  the  hydrogen  of  the  acid  is  displaced  and  liber- 
ated  as   free   hydrogen,   as   when   zinc   or   iron   is   dissolved   in 
sulphuric  or  hydrochloric  acid,  or  aluminum  in  hydrochloric  acid, 
or  iron  in  phosphoric  acid. 

When  copper  is  dissolved  in  sulphuric  acid  the  reaction  is : 

Cu+2H2SO4=CuSO4+2H2O+SO2. 

Similar  reactions  occur  when  silver  and  mercury  are  treated 
with  sulphuric  acid ;  these  reactions  include  oxidation  and  reduc- 
tion as  well  as  substitution.  As  sulphuric  acid  is  (HO)2SO2,  it 
will  be  seen  that  the  metal  is  oxidized  at  the  expense  of  the  sul- 
phur the  polarity-value  of  which  is  reduced  from  -\-6  to  +4  and 

117 


Il8  CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 

the  hydrogen  of  the  sulphuric  acid  which  contributes  the  sulphate 
radical  toward  the  formation  of  the  copper  sulphate  and  the  two 
hydroxyls  of  the  molecule  of  sulphuric  acid  which  is  reduced  to 
SO2  form,  together,  the  two  molecules  of  water. 

When  silver,  mercury,  copper,  lead,  or  bismuth,  is  dissolved 
in  nitric  acid  we  have  again  a  similar  condition — reactions  in- 
cluding both  substitution  and  oxidation : 

Bi+4HONO2=Bi  ( NO3)  3+2H2O+NO, 
or,  to  trace  the  interchanges  more  clearly : 
Bi+HONO2+3HNO3=Bi(NO3)3+HOH+NO+H2O. 

When  metallic  oxides  are  dissolved  in  acids  the  bye-product  is 
water  formed  by  the  hydrogen  of  the  acid  with  the  oxygen  of  the 
oxide : 

ZnO+H2SO4= ZnSO4+H2O. 

When  metallic  hydroxides  are  dissolved  in  acids  the  bye-prod- 
uct is  again  water,  but  twice  as  much  water  is  then  formed  as 
when  the  oxide  is  used : 

Zn(OH)2+H2SO4=ZnSO4+2H2O. 

When  acids  are  saturated  with  metallic  carbonates  two  bye- 
products  are  formed,  namely  water  and  carbon  dioxide,  because 
carbonic  acid  as  soon  as  formed  breaks  up  into  H2O  and  CO2 : 

CaCO3+2HNO3=Ca  ( NO3)  2+H2O+CO2. 

208.  The  acids  or  other  chemical  solvents  are  said  to  be  "neu- 
tralized" or  "saturated"  by  the  metal  or  metallic  compound  dis- 
solved, and  these  expressions  are  used  because  the  point  of 
neutralization  or  saturation  is  frequently  determined  by  the  aid 
of  "test-paper." 

But  in  many  cases  the  acid  may  be  completely  saturated  by 
adding  to  it  an  excess  of  the  metal  or  metallic  compound.  This 
can  be  safely  done  whenever  there  is  no  danger  of  the  formation 


CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 

of  meta-compotmds  or  basic  salts,  or  other  undesired  products. 
It  is  safe  to  saturate  sulphuric  acid  with  zinc,  iron,  or  copper, 
or  hydrochloric  acid  with  iron  or  zinc,  or  nitric  acid  with  silver, 
lead  or  copper ;  but  if  salts  of  normal  composition  are  sought  nitric 
acid  can  not  be  saturated  by  mercury  used  in  excess,  or  acetic 
acid  by  lead  in  excess. 

209.  In  Chapter  XIX,  Vol.  I,  we  have  seen  that  the  products 
of  chemical  solution  [except  gases  which  escape]  must  be  soluble 
in  the  liquid  in  which  the  reactions  take  place ;  that  acids  do  not 
dissolve  metals  and  metallic  compounds  unless  they  form  water- 
soluble  salts  with  them  [or  salts  soluble  in  the  acid  itself  if  the 
acid  is  strong  or  used  in  excess] . 

When  the  salt  formed  is  not  soluble  in  water  but  soluble  in 
the  acid,  then  a  diluted  acid  can  not  be  successfully  employed 
unless  used  in  considerable  excess,  and  the  result  will  then  be  a 
solution  containing  much  free  acid.  Solutions  of  antimony 
chloride  and  of  the  nitrates  of  mercury  and  bismuth  in  water 
without  the  presence  of  much  free  acid  can  not  be  produced ;  but 
solutions  of  these  compounds  containing  large  proportions  of  the 
acids  are  made  and  are  useful  for  certain  purposes. 

When  the  salt  formed  is  quite  soluble  in  water  and  in  the  dilute 
acid  but  insoluble  in  concentrated  acid,  then  the  undiluted  acid 
does  not  dissolve  the  metal. 

210.  The  action  of  the  heavy  metals  upon  the  common  inor- 
ganic acids.     Gold  and  the  platinum  metals  do  not  attack  any  acid, 
but  they  dissolve  in  nitrohydrochloric  acid  or  aqua  regia,  forming 
chlorides  with  the  free  chlorine. 

Aluminum  decomposes  hydrochloric  acid,  forming  aluminum 
chloride  and  setting  the  hydrogen  free.  It  does  not  attack  other 
acids. 

Antimony  is  oxidized  by  strong  nitric  acid  to  insoluble  anti- 
monous  oxide.  Other  acids  are  not  affected  by  antimony. 

Tin  decomposes  strong  nitric  acid,  forming  metastannic  acid. 
It  also  decomposes  hydrochloric  acid,  forming  stannous  chloride. 
Sulphuric  acid  is  not  decomposed  by  tin. 

Bismuth  quickly  decomposes  nitric  acid,  forming  bismuth  ni- 
trate, and  it  also  attacks  hot  concentrated  sulphuric  acid,  but  not 
hydrochloric  acid. 

Silver  attacks  dilute  nitric  acid,  forming  silver  nitrate ;  it  also 


120  CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 

decomposes  hot  concentrated  sulphuric  acid.  It  does  not  act  upon 
hydrochloric  acid. 

Lead  decomposes  nitric  acid,  but  scarcely  affects  hydrochloric 
and  sulphuric  acid. 

Copper  vigorously  attacks  nitric  acid  and  also  decomposes  hot, 
strong  sulphuric  acid,  but  is  not  dissolved  in  hydrochloric  acid  or 
diluted  sulphuric  acid. 

Nickel  decomposes  hydrochloric  acid,  sulphuric  acid  and  nitric 
acid,  forming  nickelous  salts. 

Iron  and  sine  readily  decompose  the  diluted  acids. 

211.  Hydrochloric  acid  dissolves  zinc,  aluminum,  iron,  nickel 
and  tin;  it  does  not  dissolve  lead,  copper,  mercury,  silver,  gold, 
platinum,  arsenic,  antimony  and  bismuth. 

Diluted  sulphuric  acid  dissolves  zinc,  iron  and  nickel.  Hydro- 
gen is  set  free.  But 'it  does  not  dissolve  aluminum,  lead,  copper, 
mercury,  silver,  gold,  platinum,  tin,  arsenic  antimony  and  bis- 
muth. . 

Concentrated  sulphuric  acid  dissolves  copper,  and,  if  hot,  it  is 
also  attacked  by  mercury,  silver  and  bismuth. 

The  acid  not  entering  into  the  formation  of  the  sulphate  is 
reduced  to  SO2. 

Moderately  dilute  nitric  acid,  especially  when  warm,  dissolves 
zinc,  iron,  nickel,  lead,  copper,  mercury,  silver,  arsenic  and  bis- 
muth. Arsenic  is  oxidized  to  arsenic  acid ;  the  other  metals  form 
nitrates.  The  acid  not  entering  into  the  nitrate  is  reduced  to  NO, 
which  oxidizes  in  the  air  to  red  vapors  of  N2O4,  or  NO2,  or  both, 
according  to  the  temperature. 

Cold  and  very  dilute  nitric  acid  dissolves  iron  and  zinc,  forming 
ferrous  nitrate  or  zinc  nitrate  together  with  ammonium  nitrate. 

Concentrated  nitric  acid  is  not  attacked  by  iron,  but  dissolves 
lead,  copper,  mercury,  silver,  arsenic  and  bismuth.  It  is  not  af- 
fected by  gold  and  platinum.  It  oxidizes  tin  to  insoluble  meta- 
stannic  acid,  and  antimony  to  insoluble  antimonous  oxide. 

212.  The   foregoing  statements  are   not  to  be  construed  to 
mean  that  metals  which  are  not  dissolved  by  the  acids  named 
may  not  be  superficially  affected  to  a  considerable  degree.    Diluted 
sulphuric  acid  does  take  up  copper  and  form  copper  sulphate  so 
that  copper  vessels  are  corroded  by  it ;  but  the  diluted  acid  dis- 
solves the  metal  so  slowly  and  to  such  a  limited  extent  that  we 
would  not  use  diluted  sulphuric  acid  for  such  a  purpose,  but  con- 


CHEMICAL    SOLUTION WET    OXIDATION,    ETC.  121 

centrated  acid  instead.  [Tin  is  not  affected  by  sulphuric  acid,  but 
tinned  iron  or  tin  plate,  however  heavily  coated  with  pure  tin,  is 
comparatively  soon  destroyed  by  not  only  very  dilute  sulphuric 
acid  but  even  by  boric  acid  solutions  and  by  very  weak  acetic 
acid,  probably  because  the  tin  coating  is  not  so  impervious  that 
the  iron  is  absolutely  protected.] 

213.  Metallic  sulphides  are  soluble  in  acids  if  their  metals  are 
such  as  perform  strongly  basic  functions.    Metallic  sulphides  cor- 
responding to  the  acidic  oxides  are  insoluble  in  dilute  acids,  but 
soluble  in  alkali  solutions,  as,  for  instance,  the  sulphides  of  arsenic 
and  antimony.     As  zinc  hydroxide  is  soluble  in  acids  as  well  as 
in  strong  alkali  solutions,   its    corresponding    sulphide    is  also 
soluble  in  both  acids  and  alkalies.     Antimony  sulphide  dissolves 
in  very  concentrated  hydrochloric  acid,   forming  antimony  tri- 
chloride and  hydrogen  sulphide ;  but  is  not  soluble  in  dilute  hy- 
drochloric acid. 

214.  Carbonates,  sulphites  and  nitrites  of  the  metals  are  de- 
composed by  all  of  the.  stronger  acids  because  they  yield  gaseous 
bye-products.     The  acid-soluble  sulphides  also  yield  a  gaseous 
bye-product,  H2S. 

215.  In  chemical  solution  the  salt  or  other  soluble  product 
formed   by   the   reaction   accumulates   in  the   solution   so  as  to 
gradually  weaken  the  solvent  and  hinder  if  not  entirely  arrest 
the  interaction.     The  products  are  not  "removed  from  the  arena 
of  the  chemical  action"  to  as  great  an  extent  as  in  precipitation, 
and  the  factors  in  chemical  solution  are  not  both  of  them  liquids 
in  all  cases.     In  most  instances  of  chemical  solution,  only  one 
of  the  factors  is  a  liquid  and  the  other  usually  a  solid  (rarely  a 
gas).     Hence  the  velocity  of  the  reaction  in  chemical  solution, 
while  it  may  be  great  at  first,  may  become  so  retarded  later  as 
to   require   acceleration  by  the   application   of   heat.     Zinc   dis- 
solves quite  rapidly  in  dilute  sulphuric  acid  until  the  solution 
contains  much  zinc  sulphate  and  but  little  sulphuric  acid  is  left ; 
after  that  point  has  been  reached  the  action  is  very  slow,  and, 
if  it  is  desired  to  completely  saturate  all  of  the  sulphuric  acid, 
heat  must  be  applied. 

The  usual  method,  when  the  bye-product  is  hydrogen,  or  car- 
bonic acid,  or  any  other  gas,  is  to  let  the  action  go  on  without 
the  aid  of  heat  until  effervescence  has  ceased,  and  then  to  apply 


122  CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 

heat  when  the  evolution  of  gas  begins  again  and  continues  until 
saturation  is  completely  effected. 

216.  Neutralisation  is  effected  in  solutions  by  mixing  acids 
and  alkalies  in  the  requisite  proportions,  adding  either  the  acid 
to   the   alkali   or   the   alkali   to   the   acid.     Acid   salts   are   also 
neutralized  by  alkalies,  and  the  alkali  carbonates  are  employed 
almost  as  much  as  the  alkali  hydroxides.     Whenever  practicable 
the  point  of  exact  neutralization  is  determined  by  a  color  reagent, 
and  the  most  common  and  useful  reagent  of  this  kind  and  for 
this  purpose  is  litmus,  which  is  generally  employed  in  the  form 
of  litmus  paper. 

Litmus  is  a  blue  pigment  prepared  from  certain  lichens.  It  is 
turned  red  by  acids ;  alkalies  restore  the  blue  color.  White  un- 
sized paper  dipped  in  a  solution  of  litmus  and  dried  is  called 
litmus  paper,  or  test-paper.  The  blue  litmus  paper  is  made  from 
the  unaltered  solution  of  the  pigment;  the  red  litmus  paper  is 
made  from  a  litmus  solution  to  which  just  enough  dilute  hydro- 
chloric acid  has  been  added  to  turn  its  color  red. 

A  liquid  which  turns  blue  litmus  paper  red  is  said  to  have  an 
acid  reaction;  one  that  turns  red  litmus  paper  blue  has  an  alkaline 
reaction ;  a  liquid  which  does  not  change  the  color  of  either  red  or 
blue  litmus  paper  is  said  to  have  a  neutral  reaction  on  test-paper 
or  to  be  neutral  to  test-paper.  The  test  is  made  by  touching  a 
small  strip  of  the  test-paper  with  the  liquid,  or  the  liquid  with  the 
test-paper. 

In  testing  liquids  with  litmus  paper  it  is  necessary  to  guard 
against  interferences  which  might  vitiate  the  test  or  mislead  the 
operator.  It  is  quite  possible,  for  instance,  to  conclude  from  the 
acid  reaction  of  a  liquid  which  contains  a  little  carbonic  acid 
that  the  salt  in  solution  is  an  acid  salt  when  in  reality  it  may 
be  perfectly  neutral ;  this  may  occur  when  an  acid  is  being  neutral- 
ized with  a  carbonate.  When  a  salt  of  acid  reaction  is  being 
decomposed  with  ammonia,  or  an  acid  neutralized  with  it,  the 
litmus  paper  may  show  an  alkaline  reaction  produced  by  the 
ammonia  vapor  above  the  liquid  while  the  liquid  itself  is  still 
slightly  acid  or  neutral. 

217.  When  a  strong  acid  is  neutralized  with  a  strong  base,  the 
salt  formed  is  a  normal  salt.     But  normal  salts  formed  by  strong 
acids  with  weak  bases  have  an  acid  reaction,  and  those  formed 
by  weak  acids  with  strong  bases  have  an  alkaline  reaction.     Even 


CHEMICAL    SOLUTION WET    OXIDATION,    ETC.  123 

acid  salts  (salts  still  containing  some  of  the  replaceable  hydrogen 
of  the  acid)  may  have  a  decidedly  alkaline  reaction  as  we  find 
to  be  the  case  with  the  bicarbonates  of  potassium,  sodium  and 
ammonium ;  and  so-called  basic  salts  may  have  an  acid  reaction  as 
is  the  case  with  solutions  of  subsulphate  of  iron.  Several  salts 
(notably  sulphates  and  nitrates)  of  aluminum,  iron,  zinc,  copper, 
and  other  metals  have  an  acid  reaction  although  their  composition 
is  normal.  Even  alum  has  an  acid  reaction. 

218.  When  acids  are  saturated  with  the  metals  or  with  metallic 
oxides,  hydroxides  or  carbonates  the  proportions  employed  of 
the  materials  are  determined  beforehand,  even  if  an  excess  of 
the  metal  or  metallic  compound  is  to  be  used,  and  when  salts  of 
normal  composition  are  to  be  prepared  and  the  reaction  on  test- 
paper  does  not  indicate  the  composition,  the  exact  theoretical  pro- 
portions are  used. 

219.  The  salts  prepared  by  chemical  solution,  if  crystallizable, 
are  always  recovered  by  crystallization  because  this  method  in- 
sures a  product  of  definite  composition  and  fine  appearance  if 
the  process  is  well  managed. 

Many  salts  of  the  heavy  metals  crystallize  most  readily  and 
satisfactorily  and  of  perfectly  normal  composition  from  strongly 
acidulated  solutions.  Solutions  of  the  sulphates  are  acidulated 
with  sulphuric  acid,  those  of  nitrates  with  nitric  acid,  acetates 
with  acetic  acid,  chlorides  with  hydrochloric  acid. 

Salts  of  the  alkali  metals,  on  the  other  hand,  sometimes  crystal- 
lize most  readily  from  alkaline  solutions.  Solutions  of  potas- 
sium salts  are  rendered  alkaline  by  the  addition  of  a  little  car- 
bonate or  hydroxide  of  potassium,  and  solutions  of  sodium  salts 
with  sodium  carbonate  or  hydroxide ;  solutions  of  ammonium  salts 
are  rendered  alkaline  with  ammonia  water. 

But  there  are  so  many  exceptions  to  these  general  statements 
that  no  inexperienced  operator  can  be  guided  by  them;  special 
directions  in  individual  cases  are,  therefore,  given  in  all  com- 
plete working-formulas. 

220.  Amorphous  salts,  and  those  that  can  not  be  advantage- 
ously produced  in  large  crystals,  are  recovered  from  solutions 
obtained   by  chemical    solution,   by  turbidation,    granulation   or 
evaporation  to  dryness,  or  by  evaporation  until  a  moist  salt  resi- 
due is  obtained,  which  is  then  spread  out  on  plates  to  dry. 

221.  In  addition  to  the  examples  already  given  we  shall  men- 


124  CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 

tion  now  a  sufficient  number  of  instances  of  chemical  solution 
to  show  how  varied  such  processes  are :  The  production  of  phos- 
phoric acid  by  dissolving  phosphorus  in  nitric  acid  is  an  oxida- 
tion process  and  at  the  same  time  chemical  solution ;  the  produc- 
tion of  Rochelle  salt  (tartrate  of  potassium  and  sodium)  from 
potassium  bitartrate  (acid  tartrate)  and  sodium  carbonate  is  a 
process  of  chemical  solution  (neutralization)  ;  the  production  of 
ferrous  iodide  by  dissolving  iron  and  iodine  together  in  water; 
the  solution  of  zinc  in  hydrochloric  acid  to  make  zinc  chloride ; 
the  solution  of  lead  oxide  in  a  solution  of  lead  acetate  to  make 
solution  of  subacetate  of  lead ;  making  solution  of  ferric  citrate 
from  ferric  hydroxide,  citric  acid  and  water ;  the  production  of 
soluble  ferric  phosphate  by  dissolving  precipitated  ferric  phos- 
phate in  a  solution  of  citrate  of  ammonium,  or  by  boiling  so- 
dium phosphate  and  solution  of  ferric  citrate  together ;  all  of  the 
processes  by  which  the  "scale  salts"  are  made;  the  preparation  of 
solution  of  potassium  arsenite  from  arsenous  oxide  and  potas- 
sium bicarbonate ;  the  solution  of  ammonia  gas  in  water  to  make 
the  solution  of  ammonium  hydroxide  called  ammonia  water ;  the 
solution  of  carbon  dioxide  in  water  to  produce  a  solution  of  car- 
bonic acid ;  the  preparation  of  solution  of  calcium  hydroxide  from 
calcium  oxide  (lime)  and  water;  the  formation  of  hydrogen  di- 
oxide by  dissolving  barium  dioxide  in  water. 

222.  By  the  term  wet  oxidation  I  designate  oxidation  pro- 
duced in  the  wet  way — that  is,  in  liquids.  Wet  oxidation  is 
closely  related  to  chemical  solution,  and  in  many  cases  is  nothing 
else.  As  examples  of  wet  oxidation  we  may  mention:  the 
method  of  turning  ferrous  salts  into  ferric  by  heating  their  solu- 
tions with  nitric  acid ;  making  phosphoric  acid  from  phosphorus 
with  nitric  acid;  changing  ferrous  compounds  into  ferric  by 
adding  chlorine  water,  or  by  conducting  a  current  of  chlorine  into 
the  solutions  containing  them;  producing  potassium  chlorate  by 
the  action  of  chlorine  on  potassium  hydroxide  in  solution;  pro- 
ducing potassium  permanganate  by  the  action  of  potassium 
chlorate  and  potassium  hydroxide  upon  manganese  dioxide,  etc. 

In  pharmaceutical  operations  the  most  useful  oxidizing  agents 
are  those  that  yield  bye-products  which  can  be  easily  eliminated 
or  which  are  unobjectionable.  Nitric  acid  is,  therefore,  much 
used. 

In  wet  oxidation  by  nitric  acid  heat  is  generally  applied  to 


CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 


125 


facilitate  the  reaction  and  to  expel  the  nitrogen  oxide.  The  re- 
ducing agent  is  generally  added  in  portions  to  the  acid,  and  the 
red  nitrous  vapor  is  expelled  after  each  addition  before  another 
portion  of  the  reducing  agent  is  added.  Strong  solutions  favor 
rapid  oxidation.  But  as  the  nitrous  vapor  is  very  suffocating  and 
dangerous  to  inhale,  these  operations  must  be  carried  out  under 
effective  hoods,  or  in  fume  chambers,  or  out  in  the  open  air, 
where  the  vapors  may  be  carried  away  from  the  operator  and  the 
air  he  must  breathe. 

223.  Wet  gas  operations  of  various  kinds  are  of  common 
occurrence  in  laboratories,  and  may  be  appropriately  mentioned 
here  because  they  are  intimately 
related  to  chemical  solution  and 
wet  oxidation,  frequently  includ- 
ing both. 

Hydrogen,  nitrogen,  chlorine, 
hydrogen  sulphide,  carbon  di- 
oxide, sulphur  dioxide,  nitrous 
acid,  and  various  other  gases 
are  often  produced  in  the  wet 
way  and  most  of  them  in  no 
other  way. 

The  generators  used  for  this 
purpose  may  be  ordinary  wide- 
mouthed  bottles,  or  flasks,  or 
Woulff's  bottles,  or  specially 
constructed  apparatus  such  as 
shown  in  the  illustrations. 

The  Kipp  apparatus,  as  shown 
here  or  modified  for  special  pur-  Fie-  s9..Kipp  apparatus, 

poses  according  to  circumstances,  is  very  useful  for  the  produc- 
tion of  gases  as  required  for  laboratory  use.  It  may  be  em- 
ployed for  generating  currents  of  hydrogen,  oxygen,  chlorine, 
hydrogen  sulphide,  carbon  dioxide,  and  nitric  oxide.  For  the 
evolution  of  these  several  gases  the  following  named  materials 
are  placed  in  the  bulbs:  i,  for  hydrogen  the  middle  bulb  is  to 
contain  granulated  zinc  and  the  others  a  mixture  of  I  volume 
of  sulphuric  acid  and  4  volumes  of  water ;  2,  for  oxygen  put 
pieces  of  compressed  chlorinated  lime  in  the  middle  bulb  and  a 
mixture  of  100  volumes  of  hydrogen  dioxide  and  5  volumes  of 


126 


CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 


nitric  acid  in  the  others ;  3,  for  chlorine  put  compressed  chlorinated 
lime  in  the  middle  bulb  and  a  mixture  of  7  volumes  of  hydrochloric 


Fig.  100.  Gas  evolution  apparatus. 


acid  and  5  volumes  of  water  in  the  others  ;  4,  for  generating  hydro- 
gen sulphide,  crushed  ferrous  sulphide  is  put  in  the  middle  bulb 
and  equal  volumes  of  hydrochloric  acid  and  water  in  the  others ;  5, 


Fig.  101.  Wash  bottles.     The  last  two  are  Woulff's  bottles. 

for  the  generation  of  carbon  dioxide,  broken  marble  is  put  in  the 
middle  bulb  and  equal  volumes  of  hydrochloric  acid  and  water 


CHEMICAL    SOLUTION WET    OXIDATION,    ETC. 


127 


in  the  others ;  and  6,  for  nitric  o::ide  use  copper  turnings  and  di- 
lute nitric  acid. 


Fig.  102.  Gas  evolution  apparatus. 

224.  Whenever  it  is  necessary  to  wash  the  gaseous  product 
to  remove  from  it  any  other  volatile  substances  which  may  accom- 
pany it  out  of  the  generator,  the  generator  is  connected  with 
one  or  more  wash-bottles,  and  the  gas  is,  after  having  passed 
through  the  wash-water,  conducted  into  the  receiver  where  it 
is  collected  or  dissolved  in  water.     (See  Fig.  101.) 

Volatile  acids  are  prepared  in  apparatus  similarly  constructed, 
and  the  whole  process  bears  considerable  resemblance  to  chemi- 
cal distillation.  The  fittings  necessary  are  practically  the  same 
as  used  for  small  distilling  apparatus. 

Several  -gas  solutions  are  of  considerable  importance,  as,  for 
instance,  solutions  of  chlorine,  hydrogen  sulphide,  sulphurous 
acid,  etc. 

225.  When  gas  solutions  are  made,  the  excess  of  gas  passing 
out  of  the  liquid  contained  in  the  receiving  vessel  should  be  con- 
ducted into  an  end-bottle  for  absorption  into  a  fixing-solution 
if  the  escape  of  the  gas  into  the  room  is  objectionable.     Thus  the 
excess  of  chlorine  or  of  nitric  oxide  may  be  conducted  into  a 
solution  of  sodium  carbonate.     (See  Fig.  102.) 


CHAPTER  XIV. 

THE    USES    OF    UNFINISHED    PRODUCTS PURIFICATION    OF    CRUDE 

CHEMICALS WHAT    TO    DO    WITH    DAMAGED    PRODUCTS. 

PROFITABLE  CHEMICAL  WORK. 

226.  Well-trained  pharmacists  who  have  a  moderately 
equipped  laboratory  and  make  use  of  it,  find  it  decidedly  profitable 
to  employ  unfinished  products  as  materials.  It  is  clearly  waste- 
ful and  unworkmanlike  to  adopt  an  expensive  method  of  making 
any  preparation  whenever  a  less  expensive  method  leads  to  pre- 
cisely the  same  result  as  to  the  quality  of  the  finished  article. 

Chemical  products  in  solid  form,  if  they  are  water-soluble,  are 
almost  invariably  obtained  first  in  solution,  and  are  afterwards 
recovered  from  their  solutions  by  crystallization  or  some  other 
process  frequently  involving  the  expenditure  of  considerable  time 
and  labor.  If  the  solution  contains  the  chemical  compound  of 
requisite  degree  of  purity,  and  if  all  that  remains  to  be  done  in 
order  to  finish  the  product  is  its  recovery  in  solid  form  from  the 
solution,  then  the  cost  of  that  operation  is  properly  saved  in 
every  case  where  the  solution  itself  can  be  directly  employed. 
Perfectly  pure  and  in  every  way  satisfactory  chemical  products 
in  a  state  of  solution  in  water  can  be  made  without  making  the 
solution  out  of  the  finished  solid  substance,  and  it  happens  quite 
frequently  that  liquid  preparations  are  to  be  made  containing  such 
chemical  products. 

When  a  large  quantity  of  pyrophosphate  of  iron  is  required  in 
the  form  of  water-solution  for  the  manufacture  of  some  liquid 
preparation,  the  quantity  needed  is  produced  out  of  solution  of 
ferric  sulphate,  sodium  pyrophosphate,  ammonia  water  and  citric 
acid,  or  out  of  solutions  of  ferric  citrate  and  sodium  pyrophos- 
phate, and  the  tedious  and  difficult  process  of  turning  the  pyro- 
phosphate of  iron  into  scales  is  avoided. 

If  large  quantities  of  solution  of  potassium  iodide  are  required, 
it  is  cheaper  and  quite  as  satisfactory  to  make  the  solution  out 
of  iodine,  iron  and  potassium  carbonate  instead  of  making  it  out  of 
finished  potassium  iodide. 

128 


THE    USES    OF    UNFINISHED    PRODUCTS.  I2Q 

Nothing  is  gained  by  making  a  solution  of  sodium  salicylate  out 
of  the  finished  salt  instead  of  making  it  at  less  cost  out  of  salicylic 
acid  and  sodium  bicarbonate. 

In  the  manufacture  of  elixirs,  wines,  and  other  liquid  prepara- 
tions containing  pepsin,  it  is  wasteful  to  use  finished  pepsin  since 
a  perfectly  satisfactory  solution  of  pepsin  of  ascertained  strength 
can  be  made  and  the  cost  of  scaling  the  pepsin  saved. 

Elixir  of  ammonium  valerate  can  be  produced  more  economic- 
ally out  of  a  solution  made  of  valeric  acid  and  ammonia-water 
than  out  of  crystallized  ammonium  valerate,  and  the  finished 
elixir  is,  of  course,  precisely  the  same  whether  prepared  one 
way  or  the  other. 

Scarcely  any  class  of  preparations  has  taxed  the  capital  and 
patience  of  the  pharmacist  more  severely  than  the  ''elixirs. "  They 
represent  an  almost  endless  variety  of  combinations  of  compara- 
tively few  medicinal  substances,  among  which  are  citrate  of  iron 
and  ammonium,  soluble  phosphate  of  iron,  soluble  pyrophos- 
phate  of  iron,  quinine,  strychnine,  pepsin,  citrate  of  bismuth  and 
ammonium,  etc.  To  keep  in  stock  all  of  the  different  finished 
elixirs  which  are  prescribed  containing  these  substances  requires 
very  considerable  capital.  Moreover,  it  is  practically  impossible 
for  the  pharmacist  to  determine  the  age  and  actual  condition  of 
such  preparations  with  any  degree  of  certainty;  he  is  practically 
reduced  to  the  necessity  of  accepting  them  from  the  makers  or 
dealers  if  they  only  seem  to  be  right.  And  yet  no  medicinal 
preparations  are  more  liable  to  rapid  deterioration,  so  that  they 
should  always  be  recently  prepared  in  order  to  be  satisfactory. 
The  skilled  pharmacist,  therefore,  prepares  the  elixirs  required  to 
meet  the  demands  upon  his  own  establishment,  as  far  as  practic- 
able, and,  instead  of  keeping  in  stock  a  large  variety  of  ready- 
made  elixirs  of  which  no  one  (not  even  the  manufacturer  after 
the  product  has  left  his  laboratory)  can  possess  or  acquire  suf- 
ficiently definite  and  complete  knowledge,  he  may  at  less  cost  sup- 
ply more  reliable  preparations  by  preparing  them  himself  when- 
ever required.  This  he  can  do  by  having  on  hand  recently  pre- 
pared solutions  of  the  several  medicinal  substances  named,  these 
solutions  being  so  made  that  they  are  any  and  all  of  them  mis- 
cible  with  each  other  so  that  any  combination  whatever  of  them 
can  without  any  difficulty  be  made  whenever  required  by  simply 
mixing  the  solutions  in  the  requisite  proportions  with  an  ap- 

Vol.   II— 9 


130  THE    USES    OF    UNFINISHED    PRODUCTS. 

propriately  flavored  and  sweetened  simple  elixir  of  proper  alco- 
holic strength  to  produce  the  desired  result. 

The  foregoing  illustrations  are  sufficient  to  demonstrate  the 
value  of  technical  education  for  the  practice  of  pharmacy.  But 
no  person  ignorant  of  pharmaceutical  chemistry  should  under- 
take to  do  any  such  work  because  he  could  not  know  whether  his 
results  be  right  or  wrong. 

227.  The   purification   of   crude   commercial   chemicals   is   a 
not  inconsiderable  part  of  the  profitable  work  of  the  pharmacist. 
Among  the  common  crude   inorganic  chemicals   which  can  be 
easily  purified  so  as  to  be  rendered  fit  for  pharmaceutical  and 
medicinal  use  we.  may  mention,  by  way  of  illustration:    boric 
acid,  alum,  ammonium  chloride,  copper  sulphate,  ferrous  sulphate, 
lead  acetate,  lead  nitrate,  potassium  chlorate,  potassium  nitrate, 
sodium  carbonate,  sodium  thiosulphate,  sodium  phosphate,  zinc 
sulphate.     The  cost  of  purification  of  these  and  many  other  sub- 
stances is  little  or  nothing  beyond  the  value  of  the  time  and  labor. 

Brief  general  reference  has  been  made  in  various  places  in 
this  book  to  the  purification  of  fusible  solids  contaminated  with 
infusible  impurities ;  the  purification  of  volatile  solids  by  sublima- 
tion to  remove  fixed  impurities,  and  the  removal  of  volatile  im- 
purities from  fixed  solids  by  ignition;  the  purification  of  crys- 
tallizable  soluble  substances  by  recrystallization,  turbidation, 
granulation  and  physical  precipitation ;  the  removal  of  insoluble 
substances  from  soluble  solids  by  solution  and. filtration;  the  sep- 
aration of  crystalloids  and  colloids  by  dialysis ;  the  purification 
of  liquids  by  filtration  and  by  distillation ;  and  the  precipitation 
of  foreign  substances  from  solutions  of  various  chemical  com- 
pounds by  substitution  (as  when  zinc  precipitates  iron)  or  by 
metathesis. 

Many  individual  examples  of  the  purification  of  crude  chemi- 
cal products  will  be  found  in  Part  II  of  this  volume. 

228.  Chemical  products  which  have  been  damaged  or  altered, 
or  mixed  with  other  substances  by  accident,  may  generally  be 
restored  to  their  original  condition,  or  rendered  quite  pure,  or 
converted  into  some  other  valuable  product,  by  simple  methods. 

A  crystallized  salt  which  has  effloresced,  or  which  has  under- 
gone aqueous  fusion  in  hot  weather;  a  hygroscopic  or  deli- 
quescent substance  which  has  absorbed  moisture  so  that  it  is  no 
longer  in  fit  condition  to  be  used;  a  ferrous  salt  which  has 


THE    USES    OF    UNFINISHED    PRODUCTS.  I          13! 

become  partially  oxidized  to  ferric;  a  compound  of  silvfer,  gold 
or  mercury,  or  any  other  valuable  substance  which 
partial  decomposition  from  exposure  to  light;  a  salt  accientally 
dropped  on  the  ground  and  thus  rendered  dirty  ;Vany  substance 
ruined  by  admixture  with  any  other  substance ;  SL  solid  containing 
minute  fragments  of  glass  from  a  broken  container — none  of 
these  things  cease  to  have  some  value,f  atodUipy  good  pharma- 
ceutical chemist  should  know  how  to  ^epai^  damages  of  this 
kind  or  to  reduce  the  loss  to  a  minimum.  /  rroducts  which  are 
found  impure  or  otherwise  unfit  jfor  tftiY  use  for  which  thew 
were  intended  may  frequently  be  rqpd|^ed  fit  for  other  use&yr  I 

[iscusred  in 


The  restoration  of  altered  chemXcafs  is  further  discu 
Chapter  XV.  \          /  U  V 

229.  The  pharmacist   should  mrtlWt-^De  able  to  prepare  arx^_ 
any  time,  in  an  emergency  or  a«^T  part  of  his  regular'occupation, 
almost   any   one   of   the   many  "small   chemicals  A/ which   he   is 
called  upon  to  dispense,  especially  if  he  be  locj&yd  too  far  away 
from  the  usual  sources  fcf/supply^o  j|e  abla\  A)  procure  quickly 
whatever  is  wanted,    lie)  may  often  yerable  to  make  the  prepara- 
tion in  much  less  time  than  is  requirJk^To  obtain  it  from  any 
other  source.     Many ^  chemical  pnoyuctV  which  can  be  quickly 
and  easily  priparM  may  be  so  rtirmy  called  for  that  they  are 
not  easily  promwable   in  any   other  Jway.      But  even  the  most 
common  substajrflces  may  be  out  of  re^ch  when  most  wanted  and 
may  be  oi  si\cji  Vature  that  it  is  easier  to  make  them  than  to 
send   for  mejn.     Mnally,   it   has  been  frequently  demonstrated 

in  the  laboratories  of  well  equipped  pharmaceutical  schools  that 
newer  and  rarer  chemical  preparations,  organic  and 
inorganic/,  for  which  very  high  prices  are  charged  by. those  who 
supply^tnem,  chiefly  because  they  are  new,  can  be  very  readily 
made  by  the  pharmacist  himself  at  far  less  cost. 

230.  A   large   number   of   pharmaceutical    chemicals   are   of 
such  a  character  that  they  can  not  be  made  to  any  greater  ad- 
vantage on  a  large  scale  than  in  very  moderate  quantities.     All 
such  products  can  be  profitably  made  by  any  intelligent,  well- 
trained  pharmacist  of  proper  business  capacity.    An  extensive  or 
generally  well  equipped  laboratory  is  not  necessary  for  this  pur- 
pose. 

Again,  if  his  whole  time  is  not  occupied  in  other  directions 
the  ambitious  educated  pharmacist  can  hardly  find  any  technical 


132  THE    USES    OF    UNFINISHED    PRODUCTS. 

work  which  will  afford  him  greater  satisfaction  than  the  manu- 
facturing of  one  or  more  carefully  selected  chemical  products 
which  he  can  make  of  unexceptionable  quality  and  in  consider- 
able quantity.  Organic  as  well  as  inorganic  products  belong  to 
the  list  of  chemicals  which  he  can  make  it  his  special  care  to 
furnish,  and  any  such  product  can  doubtless  be  marketed 
through  the  regular  distributing  channels  at  a  remunerative 
price. 


CHAPTER  XV. 

THE    PRESERVATION    OF    MEDICINAL    SUBSTANCES. 

231.  The  principal  causes  of  alteration  in  chemical  products, 
as  these  products  are  ordinarily  kept,  are  light,  heat,  and  con- 
tact with  air  or  with  moisture.     Most  of  the  changes  which  the 
chemicals  undergo  are  slow,  and  in  many  cases  they  escape  notice 
because  not  rendered  conspicuous  by  alterations  in  color  or  other 
external  properties.     In  some   instances,  however,  the  changes 
betray  themselves  by  external  signs. 

232.  Salts  containing  water  of  crystallization  may  effloresce 
and  are  then  of  unknown  value,  as  the  quantity  of  water  lost 
can  not  be  known  until  a  chemical  determination  of  the  compo- 
sition of  the  substance  shall  have  been  made,  or  the  salt  dried 
until  it  ceases  to  lose  weight  and  attains  a  known  constant  com- 
position.     As    the    amount    of    water    which    may    be    lost    by 
efflorescence   is   in  many  cases   considerable,   it   is   evident  that 
effloresced   substances   are   under   no  circumstances  to  be  used 
for  medicinal  purposes ;  they  should  be  recrystallized  so  as  to  be 
restored   to   their   normal   composition.      Effloresced   substances 
may  be  used  in  some  cases  for  the  production  of  other  chemicals, 
but  only  by  skilled  pharmacists  or  chemists  who  can  determine 
their  exact  value  and  who  will  then  correctly  compute  the  quan- 
tity required  on  the  basis  of  that  value. 

Substances  liable  to  effloresce  are  effectively  protected  from  it 
by  keeping  them  in  tightly  closed  bottles  in  a  cool  place. 

233.  Salts  which  are  readily  water-soluble  and  contain  a  large 
proportion  of  water  of  crystallization  may,  in  very  hot  weather, 
or  when  put  in  a  hot  place,  undergo  aqueous  fusion.     When 
cooled  the  salt,  of  course,  solidifies  again,  and  if  contained  in  a 
tightly  closed  bottle  it  loses  no  water  so  that  its  composition  is 
unaltered ;  but  it  forms  a  solid  mass  in  the  bottle  from  which  it 
can  not  be  removed  except  by  dissolving  it  again  either  in  its 
own  water,  as  before,  or,  preferably,  in  more  water.     The  salt 
may   then   be   recrystallized,   or   the   solution,   made   of   definite 
strength,  can  be  employed  for  any  laboratory  operation  for  which 
it  may  be  required. 

133 


134  THE   PRESERVATION   OF    MEDICINAL  SUBSTANCES. 

234.  Hygroscopic    and    deliquescent  substances    may  absorb 
moisture,  and  if  the  exact  quantity  of  moisture  they  contain  is 
not  known  they  can  no  longer  be  used  in  the  same  proportion 
as  if 'they  were  dry ;  and  a  moist,  wet  or  liquefied  salt  may  not  be 
adapted  for  all  the  uses  to  which  the  dry  salt  is  employed  even 
if  the  percentage  of  moisture  in  it  has  been  determined  so  that 
the   correspondingly    increased    quantity   required    of   the    deli- 
quesced salt  is  known. 

The  best  plan  is  to  dry  the  substance  so  as  to  restore  it  to  its 
proper  normal  condition. 

To  prevent  the  absorption  of  moisture,  all  hygroscopic  and 
deliquescent  substances  should  be  kept  in  tightly  closed  bottles 
in  a  dry  place.  The  containers  should  not  be  too  large  in  pro- 
portion to  the  rate  of  consumption  of  the  contents. 

235.  Substances  of  complex  chemical  structure,  or  consisting 
of  molecules  composed  of  a  large  number  of  atoms,  are  generally 
less   capable   of   resisting   decomposition   than,  are   the   simpler 
chemical  compounds. 

236.  Compounds  of  elements  and  compound  radicals  of  in- 
different chemical  energy   decompose   more   readily  than   those 
formed  by  elements  of  decided  and  powerful  positive  or  nega- 
tive chemical  polarity.     Thus  the  compounds  formed  by  nitro- 
gen are  often  unstable,  as  are  also  those  of  gold,  silver,  mer- 
cury and  several  other  weak  positive  metallic  elements ;  but  com- 
pounds formed  by  the  alkali  metals  and  the  alkaline-earth  metals 
are  very  stable,  especially  when  the  negative  elements  to  which 
they  are  united  are  also  powerful  radicals.     Salts  of  weak  bases 
and  of  weak  acids  are  usually  unstable.     Metals  generally  form 
weak  acids  when  they  form  any  acids  at  all.     Elements  which 
exhibit  great  power  when  exercising  negative  polarity   (as,  for 
instance,  the  halogens)  generally  form  unstable  compounds  when 
they  assume  positive  polarity. 

237.  Compounds  containing  elements  exercising  an  unusually 
high  polarity-value  capable  of  reduction  (in  other  words,  power- 
ful oxidizing  agents),  and  compounds  containing  elements  exer- 
cising an  unusually  low  polarity-value  capable  of  augmentation 
(in  other  words,  powerful  reducing  agents),  are  less  stable  than 
compounds  made  up  of  elements  exercising  their  normal  polarity 
and  the  dominant  valence  which  they  exhibit  when  endowed  with 
that  polarity. 


THE    PRESERVATION   OF   MEDICINAL  SUBSTANCES.  135 

238.  Light  exerts  a  decided  influence  upon  a  large  number  of 
chemical  compounds,  inorganic  as  well  as  organic.  This  influence 
is  in  opposition  to  atomic  attraction,  and  its  immediate  effect  is, 
therefore,  dissociation,  accompanied  by  changes  in  the  polarity- 
value  of  two  or  more  of  the  component  atoms  of  the  molecule 
affected.  In  other  words,  light  frequently  induces  reactions  of 
oxidation  and  reduction  in  single  chemical  compounds  as  well 
as  between  two  or  more  kinds  of  molecules  in  contact  with  each 
other. 

The  use  of  "instantaneous  photography"  demonstrates  the  fact 
that  exposure  to  light  for  a  period  of  o.ooi  second  is  sufficient 
to  decompose  certain  very  sensitive  or  unstable  chemical  com- 
pounds. Most  of  the  compounds  of  the  so-called  "noble  metals" 
are  decomposed  by  strong  light,  especially  direct  sunlight,  and 
the  dissociation  wrought  by  its  influence  is  frequently  rapid. 

Preparations  of  mercury,  silver  and  gold  must  be  carefully 
protected  against  light,  and  there  are  many  other  inorganic  com- 
pounds and  preparations  which  require  similar  protection.  The 
"scale  salts  of  iron"  are  all  sensitive  to  light,  and  liquid  prep- 
arations containing  such  scale  salts  must  all  be  kept  in  the  dark 
in  order  to  prevent  their  deleterious  alteration. 

The  pharmacopoeias  name  specifically  various  medicinal  sub- 
stances which  must  be  "kept  in  a  dark  place,"  or  "kept  in  dark 
amber-colored  bottles,"  or  "protected  against  light ;"  but  the 
list  of  substances  directed  to  be  thus  protected  should  be  con- 
siderably extended.  The  following  substances  should  all  be 
carefully  protected  against  light:* 

(Benzoic  acid,  phenol,  citric  acid,  gallic  acid),  hydrobromic 
acid,  hydrochloric  acid,  hydrocyanic  acid,  nitric  acid,  nitrohy- 
drochloric  acid,  (salicylic  acid),  sulphurous  acid,  (tannic  acid, 
tartaric  acid,  acetic  ether),  ammonium  benzoate,  ammonium  io- 
dide, ammonium  valerate,  (amyl  nitrate),  sulphurated  antimony, 
(apomorphine  hydrochloride),  chlorine  water,  (all  aromatic 


*Although  the  scope  of  this  book  is  limited  to  inorganic  substances,  I 
have  included  in  this  chapter  the  organic  medicinal  substances  liable  to 
change  because  some  of  the  substances  requiring  protection  are  partly  of 
organic  and  partly  of  inorganic  origin,  and  because  the  sensitiveness  of 
organic  substances  furnishes  an  altogether  legitimate  illustration  of  the 
chemical  effects  of  light,  heat,  air,  etc.,  upon  matter  in  general.  More- 
over, this  list  may  serve  to  call  needed  attention  to  the  general  neglect  of 
this  whole  subject.  The  organic  substances  are  those  put  in  brackets. 


136  THE   PRESERVATION   OF   MEDICINAL  SUBSTANCES. 

zvaters),  all  silver  compounds,  iodide  of  arsenic,  (atropine  and  all 
its  salts),  gold  and  sodium  chloride,  bismuth  and  ammonium  cit- 
rate, (caffeine  and  citrated  caffeine,  chloral,  chloroform,  chry- 
sarobin,  cinchonidine  and  all  its  salts,  cinchonine  and  all  its 
salts,  cocaine  and  all  its  salts,  elaterin,  eucalyptol),  ferric 
chloride,  all  "scale-salts"  of  iron,  saccharated  ferrous  iodide,  fer- 
rous lactate,  ferric  valerate,  (glycerite  of  phenol,  glycerite  of 
tannic  acid),  mercuric  chloride,  calomel,  mercuric  cyanide,  the 
mercurous  and  mercuric  iodides,  the  yellow  and  the  red  oxide  of 
mercury,  yellow  mercuric  subsulphate,  ammoniated  mercury,  all 
other  mercury  compounds,  (hydrastinine  and  all  its  salts, 
hyoscine  and  all  its  salts,  hyoscyamine  and  all  its  salts,  iodoform), 
solution  of  arsenic  and  mercuric  iodide,  solution  of  ferric  acetate, 
solution  of  ferric  chloride,  solution  of  ferric  citrate,  solution  of 
ferric  nitrate,  solution  of  ferric  subsulphate,  solution  of  chlorin- 
ated soda,  lithium  benzoate,  lithium  salicylate,  (methyl  salicylate, 
morphine  and  all  its  salts,  naphtol,  paraldehyde),  phosphorus, 
(physostigmine  and  all  its  salts,  pilo  car  pine  and  all  its  salts),  lead 
iodide,  potassium  permanganate,  (pyrogallol,  quinidine  and  all  its 
salts,  quinine  and  all  its  salts,  resin  of  podophylhnn,  resorcin, 
salol,  santonin,  sodium  benzoate,  sodium  iodide,  sodium  salicylate, 
sodium  paraphenolsulphonate,  (sparteine  and  its  salts,  spirit  of 
nitrous  ether),  strontium  iodide,  (strychnine  and  all  its  salts), 
syrup  of  hydriodic  acid,  syrup  of  ferrous  iodide,  syrup  of  the 
phosphates  of  iron  quinine  and  strychnine,  (veratrine),  zinc  io- 
dide, zinc  phosphide. 

[All  alkaloids  and  alkaloidal  salts  should  be  protected  against 
light  because  experience  has  shown  that  they  are  very  generally 
sensitive  to  its  decomposing  effects.  In  fact  all  organic  chemicals 
should  be  kept  in  the  dark,  or  in  dark  amber-colored  bottles.] 

[Volatile  oils  and  oleoresins,  aromatic  waters  and  aromatic 
spirits  should  all  be  kept  in  the  dark.] 

[Fixed  oils  and  fats,  ointments,  cerates  and  plasters  also  re- 
quire protection  against  light.] 

[All  crude  organic  (vegetable)  drugs,  and  especially  their 
powders  must  be  carefully  guarded  against  exposure  to  the  dam- 
aging action  of  light,  and,  of  course,  also  the  fluid  extracts,  ex- 
tracts, tinctures,  wines,  and  syrups  of  all  plant  drugs.  All 
elixirs.  ] 

In  the  foregoing  list  the  articles  named  in  italics  were  not, 


THE   PRESERVATION    OF    MEDICINAL  SUBSTANCES.  137 

in  the  American  Pharmacopoeia  of  1890,  mentioned  as  requiring 
protection  against  light. 

Dark  amber-colored  glass,  and  any  earthenware  which  trans- 
mits no  light  whatever,  constitute  the  most  suitable  material  of 
which  containers  for  medicinal  substances  can  be  made.  Blue  or 
purple  glass,  however  dark,  is  the  most  mischievous — more  so 
than  perfectly  colorless  glass.  But  it  is  an  excellent  plan  to  put  all 
bottles  containing  substances  sensitive  to  light  into  tight  wooden 
boxes,  where  they  will  not  be  reached  by  any  light  save  when  the 
boxes  are  opened.  The  bottles  put  in  the  boxes  should  be  of  dark 
amber-colored  glass,  tightly  stoppered,  and  well  wrapped  in  thick 
black  or  dark  yellowish-brown  paper. 

239.  Heat  is  in  some  cases  nearly  as  damaging  as  light  in  its 
action  upon  compound  matter.  I  refer  now  to  such  temperatures 
as  may  be  met  with  under  ordinary  conditions  in  the  officine  or 
^work-room  of  the  pharmacist  or  in  warerooms  of  dealers  in 
drugs  and  chemicals.  No  matter  how  these  rooms  may  be  heated, 
the  temperature  is  sometimes  excessive,  especially  near  the  stove, 
registers,  or  radiators,  and  near  the  ceiling.  In  hot  climates, 
and  in  very  hot  weather  in  moderate  climates,  the  room  tempera- 
ture may  often  be  so  high  that  all  medicinal  substances  alterable  at 
temperatures  above  15°  or  20°  are  liable  to  suffer  damage  un- 
less removed  to  the  coolest  place  available.  Finally,  some  por- 
tions of  most  stores  and  work-rooms  are  so  exposed  to  the  heat 
from  the  sun  that  substances  liable  to  injury  from  light  or  heat, 
or  both,  should  never  be  placed  there. 

By  "a  cool  place"  the  pharmacopoeias  mean  a  place  where  the 
temperature  never  exceeds  15°,  and  does  not  fall  below  10°  C. 

The  substances  which  must  be  kept  in  a  cool  place  are :  I ,  very 
volatile  substances ;  2,  those  liable  to  undergo  aqueous  fusion ;  3, 
those  liable  to  efflorescence ;  4,  substances  prone  to  fermentation ; 
5,  all  fatty  substances ;  6,  all  volatile  oils ;  and  7,  unstable  sub- 
stances generally. 

Among  them  we  may  specially  mention:  Strong  acetic  acid, 
strong  nitric  acid,  ammonia  water  (these  because  they  are  con- 
centrated solutions  of  volatile  substances  so  that  full  bottles  of 
them  tightly  stoppered  and  then  kept  in  a  very  warm  place  may 
burst,  or  may  prove  dangerous  to  open  on  account  of  the  rush 
of  vapor  from  the  contents);  (oleic  acid),  sulphurous  acid, 
(lard  and  benzoinated  lard,  lanolin,  ether,  acetic  ether,  all 


138  THE   PRESERVATION   OF   MEDICINAL  SUBSTANCES. 

alcohol),  ammonium  carbonate,  ammonium  valerate,  (amyl 
nitrite,  all  ethers,  all  aromatic  waters),  chlorine  water,  hydrogen 
dioxide  solutions,  gold  and  sodium  chloride,  (benzin),  bromine, 
chlorinated  lime,  (camphor,  monobromated  camphor),  carbon  di- 
sulphide,  (all  cerates,  spermaceti,  chloral,  chloroform,  all  col- 
lodions, confections,  copaiba,  all  plasters,  eucalyptol),  ferric 
chloride,  all  "scale  salts"  of  iron,  iron  alum,  saccharated  iodide  of 
iron,  ferric  valerate,  (all  valerates,  iodoform),  iodine,  solution  of 
ferric  acetate,  solution  of  magnesium  citrate,  solution  of  magne- 
sium carbonate,  solution  of  chlorinated  soda,  Vallet's  mass,  (honey, 
honey  of  rose,  menthol,  mucilage,  all  oleates,  all  oleoresins,  all 
fixed  oils  and  fats,  all  volatile  oils,  pancreatin,  pepsin,  paralde- 
hyde),  phosphorus,  (pyroxylin),  sodium  salicylate,  sodium  sul- 
phite, (spirit  of  ether,  compound  spirit  of  ether,  spirit  of  nitrous 
ether),  spirit  of  ammonia,  (all  aromatic  spirits,  all  syrups,  tere- 
bene,  all  ointments). 

240.  Contact  with  air  is  inimical  to  substances  liable  to  oxida- 
tion, or  which  may  take  up  carbon  dioxide,  or  water  from  moist 
air,  or  which  give  up  water  of  crystallization  to  dry  air.  Sub- 
stances liable  to  undergo  fermentation  should  also  be  protected 
against  contact  with  air. 

The  most  effective  means  of  excluding  air  is  to  keep  the  sub- 
stances requiring  protection  in  small,  completely  filled,  tightly 
closed  containers  of  glass  or  porcelain.  Glass-stoppered  bottles 
are  generally  used  and  with  very  satisfactory  results.  In  some 
cases,  where  the  utmost  care  is  necessary  to  prevent  access  of  air 
and  moisture,  the  glass-stoppers  may  be  rubbed  over  with  a  uni- 
form but  very  thin  coating  of  pure  petrolatum  so  that  they  make 
a  smooth  air-tight  fit  in  the  necks  of  the  bottles. 

When  the  pharmacopoeias  direct  that  any  given  substance  shall 
be  kept  in  "small  bottles,"  the  decision  as  to  what  size  is  most 
suitable  is  left  to  the  judgment  of  the  pharmacist.  As  long  as 
the  container  is  filled  almost  to  the  complete  exclusion  of  air  and 
remains  tightly  closed,  the  contents  must  remain  effectively  pro- 
tected, no  matter  what  may  be  the  size  of  the  vessel.  But  when 
the  container  is  opened  and  the  contents  used,  a  portion  at  a  time 
being  removed,  air  is  necessarily  admitted  each  time.  A  "small 
bottle,"  then,  is  one  that  will  hold  no  greater  quantity  than  will 
certainly  be  consumed  in  a  very  short  time,  or  before  any  portion 
can  be  injured ;  and  in  a  few  cases  that  means  a  quantity  so  small 


THE   PRESERVATION   OF   MEDICINAL  SUBSTANCES.  139 

that  the  whole  of  it  is  probably  not  much  more  than  will  be  re- 
quired at  one  time.  In  a  pharmacy  where  syrup  of  ferrous  iodide 
is  so  frequently  dispensed  that  a  pound  bottle  of  it  will  be  emptied 
in  the  course  of  a  week  or  two,  an  "original  bottle"  of  that  size 
is  not  too  large;  but  if  100  Gm  of  that  syrup  is  more  than  will 
be  dispensed  in  two  weeks  then  an  original  bottle  holding  more 
than  100  Gm  is  not  "a  small  bottle"  within  the  meaning  of  the 
Pharmacopoeia.  It  is,  of  course,  far  better  to  use  stock  containers 
somewhat  too  small  for  convenience  than  it  is  to  use  containers 
that  are  at  all  too  large. 

241.  Impervious  containers  are  nearly  always  necessary  to 
the  preservation  of  medicinal  substances,  and  it  is,  therefore,  bad 
practice  to  keep  chemicals  in  containers  of  paper  or  wood.  Any 
medicinal  substance  however  inexpensive  it  may  be,  must  be  re- 
garded as  very  valuable  whenever  it  is  used  with  benefit  as  a 
remedy,  and  for  that  purpose  it  must  be  at  all  times  in  proper 
condition.  If  in  order  to  preserve  a  given  medicinal  agent  it 
should  be  necessary  to  use  a  container  the  cost  of  which  is  greater 
than  that  of  the  medicinal  substance  itself,  it  is  nevertheless  clearly 
inadmissible  to  use  a  cheaper  container.  There  is  no  valid  excuse 
for  any  deviation  from  that  principle.  In  many  pharmacies  it  is 
the  uniform  practice  to  dispense  all  medicines  so  far  as  practicable 
in  glass  stoppered  bottles,  and  corks  are  not  used.  This  may 
seem  to  occasion  in  some  cases  an  unnecessary  additional  expense 
to  the  consumer,  but  the  proportion  of  cases  in  which  it  is  de- 
cidedly best  from  the  point  of  view  of  the  welfare  of  the  patient 
is  so  great  and  the  additional  cost  is  so  trifling  that  this  practice 
deserves  universal  adoption  as  one  of  the  unwritten  laws  of  cor- 
rect pharmacy. 

When  manufacturers  of  chemical  products  put  up  their  goods 
in  paper  cartoons  or  wooden  boxes  they  generally  do  so  under 
protest  in  the  form  of  a  printed  label  which  declares  that  the 
practice  is  wrong,  and  that  the  customer  who  insists  upon  it  in 
order  to  save  the  cost  of  a  proper  container  must  take  the  re- 
sponsibility for  the  consequences. 

Corks  and  rubber  stoppers  are  very  unsatisfactory  and  objec- 
tionable. Glass-stoppered  bottles  are  now  so  inexpensive  that 
they  ought  to  be  generally  if  not  exclusively  used.  When  corks 
are  used  the  tops  of  the  containers  are  usually  covered  with  wax 


I4O  THE    PRESERVATION   OF    MEDICINAL  SUBSTANCES. 

or  paraffin  to  close  up  the  worm  holes  and  other  defects  in  the 
corks. 

242.  Among  the  substances  which  should  be  kept  in  small, 
tightly  closed  bottles  (glass-stoppered  bottles)  are: 

Hydrocyanic  acid,  sulphurous  acid,  (amyl  nitrate,  apomor- 
phine  hydrochlorate),  chlorine  water,  solution  of  hydrogen  diox- 
ide, gold  and  sodium  chloride  (chloral,  chloroform,  the  collodions, 
elaterin),  saccharated  carbonate  of  iron,  saccharated  iodide  of  iron, 
ferrous  lactate,  ferrous  sulphate,  ferric  valerate,  (glycerite  of 
tannic  acid),  mercurous  iodide,  mercuric  iodide,  yellow  mercuric 
oxide,  yellow  subsulphate  of  mercury,  ammoniated  mercury,  (hyo- 
scine  and  its  salts,  hyoscyamine  and  its  salts),  magnesia,  Vallet's 
mass,  (morphine  acetate,  the  oleates,  all  volatile  oils,  fixed  oils), 
phosphorated  oil,  (physostigmine  and  its  salts,  pilocarpine  and  its 
salts),  lead  acetate,  potassium  hydroxide,  potassium  acetate,  potas- 
sium cyanide,  sodium  bisulphite,  sodium  iodide,  (spirit  of  nitrous 
ether),  syrup  of  hydriodic  acid,  syrup  of  ferrous  iodide,  the  bro- 
mide, chloride,  iodide  and  phosphide  of  zinc. 

243.  All  strong  acids,  solutions  of  the  alkalies,  the  solid  alka- 
lies, bromine,  iodine,  and  other  substances  of  a  corrosive  nature 
or  having  a  destructive  action  on  corks,  must,  of  course,  be  kept 
in  glass-stoppered  bottles. 

244.  Moisture  affects  all  hygroscopic  and  deliquescent  sub- 
stances.   All  such  substances  must,  therefore,  be  kept  in  perfectly 
dry,  small,  tightly  closed    (well  made  glass-stoppered)   bottles. 
Potassium  hydroxide,  potassium  acetate,  carbonate,  and  cyanide, 
the  halides  of  zinc,  ferric  chloride,  and  several  other  substances 
are  of  this  class. 


CHAPTER  XVI. 

SOLUBILITIES  OF  INORGANIC  CHEMICAL  COMPOUNDS  IN  WATER  AND 

IN  ALCOHOL. 

245.  Few  if  any  students  or  even  experienced  pharmacists  are 
able  to  keep  in  their  memories  the  solubilities  of  individual  sub- 
stances.     But  any  one    having  a  moderately    retentive  memory 
may  easily  learn  and  remember  certain  general  statements  con- 
cerning the  solubilities  or  want  of  solubility  of  whole  groups  of 
compounds,  together  with  the  exceptions  to  those  general  state- 
ments.    Such  a  memorization  of  general  rules  relative  to  the 
solubilities  of  inorganic  chemical   compounds  is  of  such  great 
value  to  both  student  and  practitioner  of  pharmacy  that  a  chapter 
specially  devoted  to  this  subject  is  here  presented. 

For  this  purpose  we  shall  group  the  metallic  compounds  in 
two  different  ways,  as  has  already  been  done  in  this  book  for 
other  purposes,  namely:  I,  according  to  the  metals;  and  2,  ac- 
cording to  the  negative  radicals  with  which  the  metals  are  com- 
bined. 

SOLUBILITIES     OF     COMMON     METALLIC     COMPOUNDS     GROUPED    AC- 
CORDING TO  THE   METALS  IN  THEM. 

246.  Potassium  compounds.     All  are  water-soluble.     Most  of 
them  are  readily  soluble. 

Deliquescent  are  the — 

'Hydroxide,  carbonate, -cyanide,  phosphate, Miypophosphite,  and 
acetate  and  sulphurated  potassa. 

Readily  soluble  are — 

X  Bicarbonate,  chloride^brpmide,> iodide,  ferricyanide,xferrocyan- 
ide,>  nitrate, ~tartrate,Kitrate,  salicylate  and  benzoate,  andXRochelle 
salt. 

Less  readily  soluble  are — 
/  Sulphate,  in  .9.5  parts  of  water  at  15°. 

Dichromate,  in  10.  parts  of  water  at  15°.  \\^ 

Permanganate,  in  16.  parts  of  water  at  15°. 
/  Chlorate,  in  16.7  parts  of  water  at  15°. 

141 


142         SOLUBILITIES    OF   INORGANIC    CHEMICAL    COMPOUNDS. 

Very  sparingly  soluble — 

•  Cream  of  tartar,  in  201  parts  of  water  at  15°. 
Nearly  insoluble — 
Potassium-platinum  chloride. 

247.     Sodium   compounds.     All   are   soluble    except   the   anti- 
monite,  which  is  nearly  insoluble. 

Very  freely  soluble  are — 
/Hydroxide,;fcarbonate,xchlonde,Ab^ 

phate.  sulphite,  bisulphite,'  thiosulphate  (  "hyposulphite")  y nitrate, 
nitrite,  ^phosphate,  xhypophosphite,^arsenate,^paraphenolsulphate, 
/acetate,  tartrate,  /'citrate,    valerate,  xsalicyjate  and^benzoate  and 
Rochelle  salt. 
-  Less  readily  soluble — 

>  Bicarbonate,  in  11.3  parts  of  water  at  15°. 
y  Pyrophosphate,  in  12.  parts  of  water  at  15°.  iQ  ^ 

Xjetraborate  (borax),  in  16.  parts  of  water  at  15°. 
Bitartrate,~  sparingly. 

,248.     Lithium  compounds.    All  freely  soluble  in  water  except 
the^ carbonate,  which  dissolves  in  80  parts  of  water  at  I5°^A>^Vyv  ^JL   O'^S 

249.  Ammonium   compounds.     All   officinal   ammonium   com- 
pounds are  readily  water-soluble,  the  least  soluble  being  the  ben- 
zoate  and  the  carbonate,  which  are  each  soluble  in  5  parts  of 
water  at  15°. ^^V  ^[   .„ 

250.  Barium  salts.      Nitrate,   chloride,   bromide,   iodide,   sul- 
phide and  acetate  are  readily  soluble. 

Hydroxide  soluble  in  20  parts  of  water. 
Insoluble  are —  ^KM 

Carbonate,  phosphate,  sulphate  and  oxalate. 

251.  Strontium   salts.      Chloride,  ybromide    and  yiodide    are  c 
^^deliquescent.     ^M/V^ . ^h  JL  .    X>  ^\ 

The  acetate,  lactate  and  nitrate  are  readily  soluble. 
The  hydroxide  is  comparatively  sparingly  soluble. ^^<^- 
Insoluble  are — 
Carbonate,  phosphate,  sulphate  and  oxalate. 

252.  Calcium  compounds. 
Deliquescent  are — 

^Qil!2liie^^2IQLde,  iodide. 

Readily  soluble — 

Nitrate^iypophqsphite,  sulphite,  acetate^actate^  and  sulphur- 
ated lime.          - 

'     3i    '  v  A;-rv  1 1\^\ 


SOLUBILITIES   OF   INORGANIC    CHEMICAL   COMPOUNDS.         143 

Sparingly  soluble — 

Hydroxide,  in  from  600  to  700  parts  of  water  at  15°. 
Sulphate,  in  about  300  to  400  parts  of  water  at  15°. 
Insoluble —  ^ 

Carbonate,  oxalate,  phosphate.  \ 

253.  Magnesium  compounds.    Readily  soluble  are  the — 
Chloride,  bromide,  iodide,  nitrate^sulphate,  acetate,  lactate  and 

the  aj:id  citrate. 

Insoluble  are —          VveC\.f  \\v  K 

( )xide,  hydroxide;* carbonate,  oxalate,  phosphate. 

254.  Zinc  compounds. 
Deliquescent  are — 

•  Chloride,  bromide  and  iodide. 

Readily  soluble  are — 

Sulphate,  nitrate^acetatej^betate  and  paaaphenolsulphonate. 

Less  readily  soluble — 

Thc/yalerate.  ^    §S\ 

Insoluble —  ^ 

^  Oxide,    sulphide,    phosphide,    hydroxide,  X  carbonate,    oxalate, 
phosphate,  oleate. 

255.  Cadmium  compounds. 
Soluble  are  the — 

Chloride,  bromide,  iodide,  nitrate  and  sulphate.-' 

Insoluble  are  the — 

Oxide,  hydroxide,  sulphide,  carbonate,  oxalate,  phosphate. 

256.  Aluminum  compounds. 
Readily  soluble  are — 

Chloride,  bromide,   iodide,  nitrate,   sulphate,   acetate,  -potash- 
alum,  and  ammonia  alum. 
Insoluble  are  the —  '^vJL 

Oxide  an(J4i^droxide. 

257.  Cerium  compounds. 

Soluble  are  the  chloride,  nitrate  and  sulphate. 

Insoluble  are  the  oxide,  hydroxide,  carbonate  and^oxalate.     \ 

258.  Cobalt  compounds. 

The  cobaltous  salts  are  deliquescent. 
Insoluble  are  the —  v 

Oxides,  hydroxides  and  sulphides. 

259.  Nickel  compounds. 

Nickelous  sulphate  and  nickelous  chloride  are  soluble. 


144         SOLUBILITIES   OF   INORGANIC    CHEMICAL   COMPOUNDS. 

Oxides,  hydroxides  and  sulphide  are  insoluble. 

260.  Iron  compounds. 

Very  readily  water-soluble  are — 

Ferrous  chloride,  bromide  and  iodide. 

Ferrous  sulphate.^ 

Ferric^chloride  and  bromide. 

Ferric  nitrate,  subsulphate,  sulphate,  acetate,  and  citrate,  iron_ 
alum. 

The  Scale-Salts  of  iron  are  all  freely  soluble. 

Less  soluble — 

Ferrous  lactate  is  soluble  in  40  parts  of  water  at  15°. 

The  Insoluble  Iron  Compounds  are- 
Ferrous  and  ferric — 

Oxides^ydroxides,  sulphides,  carbonates,  oxalates;  phosphates, 
pyrophosphates,  metaphosphates]  hypophosphites. 

261.  Chromium  compounds. 
Water-soluble  are — 

Chlorides,  chromium   sulphate,  -  chromic   anhydride    (so-called 
"chromic  acid"),  potassium  chromate,  potassium  dichromate,  and 
chrome  alum. 
Insoluble  are- 
Oxide,  hydroxide. 

262.  Manganese  compounds. 
Soluble  are — 

Manganous   chloride,   bromide,   iodide,   nitrate   and    sulphate. 
Also  potassium  manganate  and  permanganate. 
Insoluble  are —  \  ^"\\"A^Iv4>_, 

The  oxides,  hydroxide,  carbonate,  oxalate,  phosphate,  sulphide. 

263.  Lead  compounds. 

The  only  water-soluble  lead  compounds  are — 
Nitmte;  acetate  and  subacetate. 

264.  Copper  compounds. 

The  only  water-soluble  cupric  compounds  are — 
Chloride,  nitrate/ sulphate  and  acetate. 

265.  Mercury  compounds. 

All  mercurous  compounds  are  insoluble  in  water;  but  mer- 
curous  nitrate  is  soluble  in  a  mixture  of  water  and  nitric  acid. 

The  only  water -soluble  mercuric  compounds  are — 
*>  Chloride  (i-|-i6),  bromide,  acetate  and  cyanide.    But  mercuric 
nitrate  is  soluble  in  a  mixture  of  nitric  acid  and  water 


SOLUBILITIES   OF   INORGANIC    CHEMICAL    COMPOUNDS.         145* 

266.  Silver  compounds. 

The  only  water-soluble  silver  salts  are  the>oiitrate  and  acetate. 

267.  Gold.     The  only  water-soluble  gold  compound  in  use  is 
the  trichloride. 

268.  Bismuth   compounds.     The   only  water-soluble   bismuth 
compound  is  the  citrate  of-bismuth  and  ammonium.  . 

But  normal  bismuth  nitrate,  which  is  decomposed  by  water 
is  soluble  in  glycerin  and  also  in  glacial  acetic  acid.     It  is 
soluble  in  a  mixture  of  nitric  acid  and  water. 

269.  Antimony  compounds. 

The  only  water-soluble  antimony  compound  is  tartrate  of 
timonyl  and  potassium  (tartar  emetic). 

But  chloride  of  antimony   is  soluble  in  a  mixture  of  hydro- 
chloric acid  and  water. 

270.  Arsenical  compounds. 
Sodium  arsenate  is  readily  soluble. 

The  arsenite  of  potassium  is  also  soluble. 
Iodide  of  arsenic  is  soluble. 
Arsemms  acid  is  sparingly  soluble. 

SOLUBILITIES     OF      COMMON      INORGANIC      CHEMICAL     COMPOUNDS 

GROUPED    ACCORDING    TO    THE    NEGATIVE    RADICALS    OF 

THEIR  MOLECULES. 

271.  Oxides.     No   metallic   oxides   are   water-soluble   except 
chromic  anhydride  and  other  oxides  that  react  with  the  water  to 
form  either  acids  or  bases ;  those  dissolve  by  "chemical  solution." 

272.  Hydroxides.     The  only  freely  zvater-soluble  metallic  hy- 
droxides are  those  of  the  alkali  metals. 

The  hydroxides  of  barium,  strontium  and  calcium  are  com- 
paratively sparingly  or  very  sparingly  soluble. 
All  other  metallic  hydroxides  are  insoluble. 

273.  Chlorides.     All  metallic  chlorides  are  water-soluble  ex- 
cept those  of  silver  and  lead,  mercurous  chloride,  and  the  chloride 
of  antimony,  which  is  decomposed  by  water  but  soluble  in  a  mix- 
ture of  hydrochloric  acid  and  water. 

Deliquescent  chlorides  are  those  of — 

Calcium,  zinc ;  also  ferric  chloride  and  platinic  chloride. 

Readily  soluble  are  the  chlorides  of — 

Vcl.    11—10 


146         SOLUBILITIES   OF   INORGANIC    CHEMICAL    COMPOUNDS. 

Potassium,    sodium,    lithium,    ammonium,   barium,    strontium, 
magnesium,  aluminum,  and  gold. 
Less  readily  soluble  is — 
Mercuric  chloride  (1  +  16). 
Insoluble — 

Silver  chloride  and  mercurous  chloride. 
Nearly  insoluble — 
Lead  chloride. 
Decomposed  by  zvater — 
Antimony  trichloride. 

274.  Bromides. 

Readily  soluble  are  the  bromides  of — 

Potassium,  sodium,  lithium,  ammonium,  barium,  strontium, 
calcium,  magnesium,  zinc,  aluminum,  and  ferrous  and  ferric  bro- 
mide. 

Soluble  are — 

Mercuric  bromide  and  bromide  of  gold. 

Insoluble — 

Bromides  of  silver  and  lead. 

Mercurous  bromide. 

275.  Iodides. 

•  Freely  soluble  are  the  iodides  of— 

Potassium,  sodium,  lithium,  ammonium,  barium,  strontium,  cal- 
cium, magnesium,  zinc,  cadmium,  ferrous  iodide,  manganous 
iodide,  and  arsenous  iodide. 

Insoluble  are  the  iodides  of— 

Silver,  lead,  mercury  (mercurous  and  mercuric). 

276.  Cyanides.       Those  of  the  alkali  metals  are  freely  soluble. 
Mercuric  cyanide  is  soluble. 

Cyanide  of  silver  is  insoluble. 

277.  Ferrocyanides  and  ferricyanides    of    the    alkali   metals 
are  -water -soluble. 

Those  of  the  heavy  metals  are  all  insoluble. 

278.  Sulphides.       Those  of  the  alkali  metals  and  the  alkaline- 
earth  metals  are  freely  water-soluble. 

All  sulphides  of  the  heavy  metals  are  insoluble. 

279.  Hypochlorites   of   the    alkali    metals    and    alkaline-earth 
metals  are  soluble. 

280.  Chlorates  of  potassium  and  sodium  are  soluble. 


SOLUBILITIES   OF   INORGANIC    CHEMICAL   COMPOUNDS.         147 

281.  Sulphites.      Those  of  potassium  and  sodium  are  readily 
soluble;  those  of  calcium  and  magnesium  less  readily  soluble. 

282.  Sulphates.      All    metallic    sulphates    are    soluble  except 
those  of  barium,  strontium,  calcium,  lead  and  mercury. 

Readily  soluble  sulphates  are  those  of— 

Sodium,  ammonium,  aluminum,  and  ferric  sulphate.  Also  the 
alums. 

Soluble  are  also  the  sulphates  of — 

Potassium,  lithium,  magnesium,  zinc,  ferrous  sulphate,  man- 
ganous  sulphate,  copper  sulphate. 

Very  sparingly  soluble — 

Calcium  sulphate. 

Insoluble  are  the  sulphates  of — 

Barium,  strontium  and  lead. 

Decomposed  by  water  is  the  sulphate  of  mercury  (mercuric). 

283.  Thiosulphates   of  potassium  and  sodium  are  freely  sol- 
uble. 

284.  Sulphurated  potassa  and  sulphurated  lime  are  very  freely 
soluble. 

285.  Nitrates.     All  are  water-soluble  except  those  of  mercury 
and  bismuth,  which  are  decomposed  by  water. 

286.  Nitrites  of  alkali  metals  are  soluble. 

287.  Phosphates,    pyrophosphates  and  metaphosphates.     The 
only  water-soluble  phosphates  are  those  of  the  alkali  metals  and 
ammonium. 

But  some  phosphates  of  the  heavy  metals  and  also  the  phos- 
phates of  the  alkaline-earth  metals  and  magnesium  are  soluble 
in  phosphoric  acid. 

Orthophosphates  of  iron  are  soluble  in  orthophosphoric  acid 
but  insoluble  in  pyrophosphoric  or  in  metaphosphoric  acid. 

Pyrophosphates  and  metaphosphates  of  iron  are  insoluble  in 
orthophosphoric  acid  but  soluble  in  metaphosphoric  acid. 

288.  Hypophosphites,      Those   of   the    alkali   metals   and   of 
calcium  are  water-soluble.     Those  of  the  heavy  metals  are  in- 
soluble. 

289.  Carbonates.     The    only    water-soluble    carbonates    are 
those  of  potassium  sodium  and  ammonium.     That  of  lithium  is 
sparingly  soluble. 

290.  Borates.     Sodium  tetraborate  (or  borax)  is  soluble. 


148          SOLUBILITIES   OF   INORGANIC    CHEMICAL    COMPOUNDS. 

291.  Metallic  acetates  are  all  water-soluble. 

292.  Valerates.     Only  those   of   potassium,    sodium,    lithium 
and  ammonium  are  soluble. 

293.  Oxalates.       Only   those   of   the   alkali   metals   and   am- 
monium are  soluble. 

294.  Tartrates.      The  normal  tartrates   of  the  alkali  metals 
and  ammonium  are  soluble;  their  bitartrates  are  sparingly  soluble. 

Tartrate  of  ferryl  and  potassium.  Tartrate  of  ferryl  and  am- 
monium, and  tartrate  of  antimonyl  and  potassium  are  soluble. 

295.  Citrates.      Those  of  the  alkali  metals,  ammonium  and 
of  iron  are  soluble. 

Magnesium  citrate  is  soluble  in  water  containing  much  citric 
acid. 

Bismuth  citrate  is  insoluble;  but  citrate  of  bismuth  and  am- 
monium is  soluble. 

296.  Lactates.       Those  of  the  alkali  metals,  calcium,  stron- 
tium, magnesium,  zinc  and  iron  are  water-soluble. 

297.  Salicylates.       Those  of  the  alkali  metals  are  alone  sol- 
uble. 

298.  Phenolsulphonates.     Those  of  the  alkali  metals,  barium, 
calcium  and  zinc  are  water-soluble. 

299.  Benzoates.      Those  of  the  alkali  metals,  ammonium  and 
calcium,  are  water-soluble. 

300.  Oleates.     Only  the  soaps  are  water-soluble. 

301.  The  student  will  find  it  useful  to  specially  memorize  the 
following : 

All  of  the  officinal  compounds  of  potassium,  sodium  and  am- 
monium are  water-soluble;  but  cream  of  tartar  is  only  very 
sparingly  soluble. 

The  hydroxides  of  potassium  sodium  and  ammonium  are 
freely  soluble.  [Lithium  hydroxide  is  soluble  in  about  14  parts 
of  water;  barium  hydroxide  (Ba(OH)2.8H2O)  dissolves  in  20 
parts  of  water;  strontium  hydroxide  (Sr(OH)2.8H2O)  is  sol- 
uble in  50  parts;  calcium  hydroxide  (Ca(OH)2)  is  soluble  in 
about  640  parts  of  water.] 

The  oxides,  hydroxides,  sulphides,  carbonates,  oxalates,  phos- 
phates (incl.  pyrophosphates  and  metaphosphates),  hypophos- 
phites,  arsenates  and  arsenites,  salicylates,  benzoates  and  oleates 
of  the  heavy  metals  are  all  insoluble. 


SOLUBILITIES   OF   INORGANIC    CHEMICAL    COMPOUNDS.         149 
ALCOHOL    SOLUBILITIES    OF    COMMON    CHEMICALS. 

302.  A  very  large  proportion  of  the  inorganic  chemical  com- 
pounds are  insoluble  in  alcohol,  and  especially  those  that  contain 
much  water  of  crystallization.     Inorganic  chemical  compounds 
which  are  insoluble  in  water  are  also,  with  scarcely  any  excep- 
tions, insoluble  in  alcohol;  but  a  large  number  of  water-soluble 
inorganic  chemicals  are  insoluble  in  alcohol. 

303.  Very  soluble  (in  less  than  5  parts  of  alcohol)  :  [Benzoic, 
citric,  salicylic,  tannic  and  tartaric  acids.] 

Hydroxides  of  potassium,  sodium  and  ammonium. 

Chlorides  of  magnesium,  zinc,  iron  (both  ferrous  and  ferric), 
and  mercuric  chloride. 

Bromides  of  lithium,  barium,  strontium,  calcium,  magnesium, 
and  zinc. 

Iodides  of  lithium,  sodium,  barium,  calcium,  magnesium  and 
zinc. 

Acetate  of  potassium. 

Valerates  of  potassium,  sodium,  ammonium  and  iron  (ferric). 

Salicylates  of  potassium,  sodium,  lithium  and  ammonium. 

Ferric  sulphate. 

304.  Soluble  in  from  6  to  30  parts  of  alcohol : 
Iodine  (i  +  io). 

Boric  acid  (1  +  15). 

Chlorides  of  lithium  (i  +  io),  strontium  (i-(-6),  calcium 
(1+8). 

Bromides  of  sodium  (1  +  13),  ammonium  (1+30),  and  mer- 
curic bromide. 

Iodides  of  potassium  (1  +  18),  ammonium  (1+9),  strontium, 
and  cadmium. 

Mercuric  cyanide  (1  +  15). 

Nitrate  of  ammonium  (1+20). 

Hypophosphite  of  potassium  (1+7.3)  an<^  sodium  (1+30). 

Acetate  of  sodium  (1+30)  and  lead  (i-J-2i). 

Lactate  of  strontium. 

Benzoate  of  lithium  (1  +  12)  and  ammonium  (1+28). 

Sparingly  soluble  (in  from  36  to  200  parts)  : 

Bromide  of  potassium  (1+200). 

Iodide,  mercuric  (1  +  130). 

Chlorate,  sodium  (i  +  ioo). 


I5O         SOLUBILITIES   OF   INORGANIC    CHEMICAL    COMPOUNDS. 

Nitrate,  sodium  (i-j-ioo). 

Bisulphite,  sodium  (1+72). 

Phenolsulphonate,  sodium  ( 1  +  132). 

Acetate,  zinc  (1+36). 

V derate,  zinc  (1+40). 

Bcnzoate,  sodium  (1+45). 

305.     Insoluble,  or  nearly  so,  in  alcohol: 

All  metallic  carbonates,  o.ralates,  phosphates,  pyrophosphates, 
metaphosphates,  ar senates,  ar senile s,  citrates  and  tartrates. 

All  metallic  sulphates  except  ferric  sulphate. 

All  the  "scale-salts"  of  iron. 

The— 

Chlorides  of  potassium,  sodium  and  ammonium,  and  mercur- 
ous  chloride. 

Iodide  of  lead  and  mercurous  iodide. 

Cyanide  of  potassium. 

Nitrates  of  potassium,  lead,  copper  and  mercury. 

Nitrate  of  sodium. 

Chlorate  of  potassium. 

Sulphite  of  sodium. 

Thiosulphate  of  sodium. 

Borax. 

Potassium  dichr ornate. 

Potassium  ferrocyanide  and  ferricyanide. 

Ammoniated  mercury. 

Ferrous  lactate. 


CHAPTER   XVII. 

THE  DENSITY  OF  SOLIDS  AND  LIQUIDS.      THE  MOHR-WESTPHAL  BAL- 
ANCE.      HYDROMETERS,    PYCNOMETERS,    ETC. 

306.  It  is  very  frequently  necessary  in  laboratory  operations 
to  take  the  density  of  various  liquids.    As  this  happens  most  fre- 
quently in  the  process  of  concentrating  solutions  by  evaporation 
preparatory  to  crystallization,  and  as  density  is  a  convenient  guide 
to  the  approximate   strength  of  solutions,   we  shall  sufficiently 
discuss  this  subject  before  we  describe  evaporation  and  crystal- 
lization. 

But  the  student  must  consult  special  works  on  weights  and 
measures,  specific  weight,  balances,  and  other  apparatus  and  in- 
struments, to  learn  the  principles  involved  in  their  construction 
and  the  details  of  their  care  and  use. ' 

307.  The  density  of  any  substance  is  the  relation  of  its  mass 
to  its  volume.     It  is  expressed  in  units  representing  the  density 
of  some  known  substance  adopted  as  the  medium  of  comparison. 
The  densities  of  solids  and  liquids  are  thus  expressed  by  num- 
bers, the  significance  of  which  is  understood  from  the  fact  that 
the  value  of  each  unit  is  the  density  of  water.     The  densities  of 
gases  or  vapors  are  compared  to  and  expressed  in  units  of  the 
density  of  hydrogen. 

The  term  specific  gravity  is  most  commonly  employed  to  ex- 
press density;  and  the  term  specific  weight  is  also  used  with  the 
same  meaning. 

Accordingly,  the  density,  specific  weight,  or  specific  gravity 
of  water,  as  these  terms  are  commonly  employed,  is  i;  and  the 
density,  specific  weight  or  specific  gravity  of  hydrogen  is  also  i. 
But  water  is  about  11,160  times  as  heavy  as  hydrogen,  so  that 
the  density  of  water  expressed  in  units  of  the  density  of  hydro- 
gen is  11,160;  and  the  density  of  hydrogen  expressed  in  units  of 
the  density  of  water  is  nlm  or  0.0000896.  These  numbers  are 
so  inconvenient  as  to  forbid  the  employment  of  the  water  unit  to 
express  the  densities  of  gases  or  of  the  hydrogen  unit  to  express 
the  densities  of  solids  and  liquids. 

151 


152  BALANCES,   HYDROMETERS,   PYCNOMETERS,   ETC. 

The  density  of  air  was  formerly  employed  (and  is  still  used  to 
a  considerable  extent)  for  expressing  the  densities  of  gases ;  but 
it  can  not  be  used  as  the  unit  of  expression  in  stating  the  densi- 
ties of  solids  and  liquids,  and  there  are  strong  reasons  in  favor  of 
the  settled  preference  for  hydrogen  as  against  air  as  the  medium 
of  comparison  of  the  densities  of  gases. 

Air  is  about  14.43  times  as  heavy  as  the  same  volume  of  hy- 
drogen, so  that  the  density  of  dry  air  in  hydrogen  units  is  about 
14.43  and  the  density  of  hydrogen  in  units  of  the  density  of  dry 
air  is  about  0.0693. 

308.  Since  inorganic  pharmaceutical   chemical   products   are 
solids  and  liquids,  it  follows  that  the  unit  of  density,  or  of  specific 
gravity,  or  specific  weight,   most  important  to  the  laborant  in 
this  field  of  work  is  the  density  of  water.     The  form  of  expres- 
sion of  the  density  of  any  given  solid  or  liquid  is,  therefore,  a 
number  which  shows  how  many  times  the  density  of  water  (the 
unit)   is  contained  in  the  density  of  that  given  solid  or  liquid. 
Thus  the  statement  that  the  density,  or  specific  weight,  or  specific 
gravity  of  any  given  solid  is  8.000  means  that  a  given  volume 
of  that  solid  weighs  8  times  as  much  as  the  same  volume  of 
water;  the  sp.  gr.  of  any  liquid  is  1.250  if  a  given  volume  of  it 
weighs  1.250  times  as  much  as  an  equal  volume  of  water;  the 
sp.  w.  of  castor  oil  is  0.960  because  one  liter  of  it  weighs  960 
Grams ;  and  one  liter  of  the  official  "solution  of  subacetate  of 
lead"  weighs  about  2.100  kilograms  because  its  density  is  2.100. 

For  the  sake  of  uniformity  and  precision  the  specific  weights 
of  all  liquids  are  expressed  in  numbers  carried  out  to  the  third 
decimal,  and  in  a  few  cases,  where  circumstances  require  it, 
even  four  decimals  are  given. 

309.  The  densities  of  all  substances  are  affected  by  tempera- 
ture, pressure,  buoyancy,  and  other  conditions.     It  is,  therefore, 
necessary  to  know  the  conditions  to  which  any  expression  of 
density   refers.      For   all   ordinary  purposes   the   standard  tem- 
perature of  15°  C.    is    almost  universally  adopted,  and  most  of 
the  pharmacopoeias  of  recent  date  state  the  specific  gravities  of 
liquids  at  15°  C.  in  numbers  which  refer  to  the  density  of  water 
at  the  same  temperature  as  the  unit  of  expression.     But  some 
pharmacopoeias  give  the  specific  gravities  of  liquids  at   15°   C. 
in  units  referring  to  the  density  of  water  at  4°  C. 

The  buoyancy  and  atmospheric  pressure  are  generally  ignored 


BALANCES,   HYDROMETERS,   PYCNOMETERS,   ETC.  153 

in  the  determination  and  expression  of  specific  gravities  for  in- 
dustrial purposes  and  in  the  pharmacopceial  tests ;  but  whenever 
scientific  accuracy  is  necessary  the  standard  unit  is  the  density  of 
water  at  4°  C.  in  vacuo,  and  the  true  density  or  specific  weight 
of  any  given  liquid  or  solid  is  the  number  which  shows  how 
many  times  the  actual  mass  (or  weight  in  vacuo)  of  a  given  vol- 
ume of  water  at  4°  C.  is  contained  in  the  actual  mass  (or  weight 
in  vacuo)  of  the  same  volume  of  that  given  liquid  or  solid  at 
the  same  temperature. 

The  Swiss  Pharmacopoeia  gives  the  true  densities  (specific 
weights  derived  from  the  true  masses  of  the  respective  liquids 
at  4°  C.)  ;  but  the  American  Pharmacopoeia,  in  common  with  the 
great  majority  of  other  pharmacopoeias  and  other  technical  work- 
ing manuals,  gives  the  apparent  densities  (specific  weights  de- 
rived from  weights  in  air  at  15°  C.)  of  the  liquids  described  in  it. 

The  difference  between  the  true  mass  of  any  liquid  or  solid 
and  its  weight  in  air  is  the  true  weight  or  mass  of  the  same 
volume  of  air. 

310.  The  law  of  archimedes,  or  the  law  of  buoyancy,  may  be 
expressed  as  follows :  Any  body  of  matter  immersed  in  any 
•fluid  [and  by  "fluid"  is  here  meant  any  liquid  or  gas]  is  pushed 
upward  by  the  gravitation  thereof  with  a  force  exactly  meas- 
ured by  the  weight  of  its  own  volume  of  that  fluid. 

A  cubic-centimeter  of  lead  resting  upon  the  table  is  immersed 
in  air;  therefore  it  does  not  press  upon  the  table  with  a  force 
equal  to  the  mass  or  true  weight  (weight  in  vacuo)  of  one  cubic- 
centimeter  of  lead,  but  with  a  force  less  than  the  mass  of  the 
metal  by  just  the  weight  of  one  cubic-centimeter  of  air.  The 
mass  of  one  cubic-decimeter  of  lead  is  11,400  Grams;  that  of 
one  cubic-decimeter  of  water  is  1,000  Grams;  that  of  one  cubic- 
decimeter  of  dry  air  is  1.29303  Grams;  that  of  one  cubic-deci- 
meter of  mercury  is  13,600  Grams;  and  that  of  one  cubic- 
decimeter  of  hydrogen  0.0896  Grams.  Consequently  it  follows 
from  the  law  of  buoyancy  that  one  cubic-decimeter  of  lead  exerts 
a  pressure  of  11,400  Grams  upon  its  support  in  a  vacuum,  but  a 
pressure  of  only  10,400  Grams  on  the  bottom  of  a  vessel  of 
water;  when  weighed  in  air  it  would  seem  to  weigh  about  11,399 
Gm,  in  hydrogen  almost  as  much  as  in  a  vacuum,  an;!,  when  sus- 
pended in  water,  only  about  10,400  Grams ;  and  if  thrown  into 
mercury  the  lead  must  float  for  it  can  sink  down  into  the  mer- 


154  BALANCES,   HYDROMETERS,   PYCNOMETERS,   ETC. 

cury  only  far  enough  to  displace  11,400  Gm   (its  own  weight) 
of  the  mercury. 

311.  Buoyancy  is  the  effect  of  gravitation,  for  mass  is  meas- 
ured by  gravitation,  density  is  the  relation  of  mass  to  volume,  and 
a  body  of  greater  density  is,  therefore,  a  body  acted  upon  by  a 
greater  force   of  gravity.     Lead  bullets  find  their  way  to  the 
bottom  of  a  basketful  of  beans  because  the  lead  is  attracted  to- 
ward the  center  of  the  earth  with  much  greater  force  than  the 
bean  substance.     Very  heavy  ores  or  other  minerals  are,  there- 
fore, sometimes  separated  from  other  substances  on  this  principle, 
as  grain  is  separated  from  the  chaff,  or  as  the  heavy  seeds  are 
separated  from  the  light  spongy  pulp  of  dried  colocynth  fruit. 

Hydrometers  and  various  other  instruments  designed  to  deter- 
mine the  specific  weights  or  densities  of  liquids  and  solids  are 
constructed  on  the  principle  of  the  law  of  buoyancy. 

312.  The  density  of  a  solid  heavier  than  water  and  unaffected 
by  it  may  be  found  as  follows:    weigh  the  solid  first  in  air  and 
then   suspended  in  water;  the  difference  is  the  weight  of  the 
same  volume  of  water,  and  the  specific  weight  of  the  solid  is 
the  quotient  found  by  dividing  its  weight  in  air  by  the  weight 
of  the  same  volume  of  water 

Should  the  solid  be  water-soluble  it  may  be  weighed  in  some 
liquid  by  which  it  is  not  affected  and  the  density  of  which  is 
known.  Let  us  suppose  that  oil  of  turpentine  is  decided  upon  as 
fulfilling  the  necessary  conditions.  The  difference  between  the 
weight  of  the  solid  in  the  air  and  its  weight  when  suspended  in 
oil  of  turpentine  is,  of  course,  the  weight  of  the  same  volume 
of  that  oil,  and  the  weight  of  the  same  volume  of  water  is  the 
quotient  obtained  by  dividing  the  weight  of  the  oil  by  its  specific 
weight.  We  then  divide  the  weight  of  the  solid  in  the  air  by 
the  weight  of  the  same  volume  of  water. 

Solids  which  are  lighter  than  water  may  be  weighed  in  lighter 
liquids,  or  they  may  be  weighted  down  with  heavy  substances  and 
thus  weighed  in  water  after  which  the  weight  of  the  water  dis- 
placed by  the  heavier  solid  is  deducted  from  the  weight  of  the 
water  displaced  by  both  solids  to  find  the  weight  of  the  water 
displaced  by  the  lighter  solid. 

But  the  volume  of  any  solid  can,  of  course,  be  readily  found 
by  submerging  it  in  any  lighter  liquid  (by  which  it  is  unaffected) 
in  a  graduated  cylinder,  for  the  rise  of  the  level  of  the  liquid 


BALANCES,    HYDROMETERS,   PYCNOMETERS,   ETC.  155 

must  correspond  exactly  to  the  volume  of  the  solid.     The  densi- 
ties of  powders  are  usually  found  by  this  means. 

The  densities  of  lard  and  other  soft  fats  and  substances  which 
can  not  be  weighed  suspended  in  liquids  may  be  found  by  plac- 
ing them  in  a  heavier  liquid  and  then  gradually  adding  a  lighter 
liquid  until  the  density  of  the  liquid  is  identical  with  that  of  the 
solid  which  may  be  known  to  be  the  case  when  the  solid  neither 
rises  to  the  surface  nor  sinks  to  the  bottom  of  the  liquid,  but  may 
be  made  to  remain  suspended  at  any  point  in  it ;  or  the  solid  may 
be  placed  in  a  lighter  liquid  after  which  a  heavier  liquid  is  added, 
until  the  densities  of  solid  and  liquid  are  equal,  as  described. 
The  solid  must  of  course  be  insoluble  in  both  liquids,  and  un- 
affected by  either  of  them,  and  the  liquids  must  be  miscible  with 
each  other  in  all  proportions. 

313.  The  densities  of  liquids  also  may  be  found  by  weighing 
solids  in  them,  since  the  apparent  loss  of  weight  of  any  solid 
when   weighed   in   any   liquid    (or   the    difference   between   the 
weight  of  the  solid  in  the  air  and  its  weight  when  suspended  in 
the  liquid)  must  be  the  weight  of  the  same  volume  of  that  liquid. 
As  the  weight  of  10  milliliters  of  water  is   10  Gm,  it  follows 
that  the  weight  of  a  piece  of  glass  measuring  10  cubic-centi- 
meters must  be  10  Gm  less  in  water  than  in  air,  and  it  must 
be  9  Gm  less  in  any  liquid  of  the  sp.   gr.  0.900,  and   12  Gm 
less  in  any  liquid  of  the  sp.  gr.  1.200. 

Thus,  a  piece  of  glass  displacing  10  milliliters  of  water  must 
lose  10  Gm  when  weighed  in  water  and  its  loss  of  weight  in 
any  other  liquid,  expressed  in  Gm,  when  divided  by  10,  must 
give  a  quotient  coincident  with  the  sp.  w.  of  that  other  liquid. 

314.  Hydrostatic  balances  are  specially  constructed  balances 
for   determining  the   specific  weights   of   liquids  and  solids  by 
weighing  solids  in  liquids. 

The  balances  of  Mohr  and  Westphal  are  the  best  hydrostatic 
balances,  and  the  most  accurate  determinations  of  specific  weight 
may  be  obtained  by  the  Mohr- Westphal  balances  (Fig.  103). 

The  solid  to  be  weighed  in  the  liquid  is  a  short  glass  ther- 
mometer suspended  from  the  end  of  the  beam  by  a  platinum  wire. 
This  thermometer  is  so  constructed  that  when  it  is  suspended 
in  air  the  balance  is  in  perfect  equilibrium.  When  the  ther- 
mometer is  suspended  in  any  liquid  in  the  cylinder,  as  shown  in 
the  cut,  it  is  buoyed  up  by  the  gravitation  of  the  liquid  so  that 


156  BALANCES,   HYDROMETERS,   PYCNOMETERS,   ETC. 

weights  are  necessary  to  restore  equilibrium ;  these  weights  show 
the  weight  of  the  liquid  displaced.  The  weights  shown  in  the 
illustration  are  "riders."  Each  smaller  rider  is  just  one-tenth 
the  weight  of  the  next  larger,  except  the  counterpoise  which 
equals  in  weight  the  water  displaced  and  which,  in  the  cut,  is 
attached  to  the  same  hook  that  supports  the  thermometer. 

As  the  product  obtained  by  multiplying  the  power  by  its  dis- 
tance from  the  fulcrum  is  equal  to  the  product  obtained  by  mul- 


0000 


Fig.  103.  The   Mohr   Westphal   balance. 

tiplying  the  load  by  its  distance  from  the  fulcrum,  it  follows  that 
when  the  distance  of  the  power  from  the  fulcrum  is  the  same 
as  the  distance  of  the  load  from  it,  the  power  and  the  load  must 
be  equal.  The  beam  of  the  balance  is  a  "lever  of  the  first  kind," 
having  the  fulcrum  between  the  power  and  the  load.  Hence, 
when  the  longer  arm  of  the  beam  or  lever  is  divided  into  ten 
equal  spaces  is  must  follow  that  any  rider  placed  in  any  given 


BALANCES,    HYDROMETERS,   PYCNOMETERS,   ETC. 


157 


1.3683 


1.7427 


1.5522 


notch  on  the  beam  must  weigh  one-tenth  more  in  that  notch  than 
it  does  in  the  next  notch  nearer  the  fulcrum.  It  is,  therefore,  im- 
material whether  or  not  the  absolute  weight  of  each  rider  is 
known  if  the  relative  weights  are  only  correct.  It  will  be  seen 
that  there  are  five  riders.  The  weights  of  the  two  largest  riders 
are  equal ;  the  third  in  size  weighs  one-tenth  as  much,  the  fourth 
weighs  one  one-hundredth, 
and  the  fifth  and  smallest 
weighs  one  one-thousandth 
as  much  as  the  largest. 

When  the  riders  have 
been  so  placed  that  the 
equilibrium  of  the  balance 
is  perfect  the  specific 
weight  of  the  liquid  can  be 
read  off  from  the  numbers 
on  the  graduated  beam. 
Should  the  liquid  be  water 
the  counterpoise  alone  will 
suffice  to  establish  equili- 
brium by  placing  it  on  the 
hook  to  which  the  platinum 
wire  is  attached ;  the  coun- 
terpoise is,  of  course,  al- 
ways used  when  the  liquid 
is  heavier  than  water,  but 
omitted  when  the  liquid  is 
lighter.  The  manner  of 
reading  the  specific  weight 
indicated  by  the  riders  is 
sufficiently  illustrated  by 
the  examples  shown  in 
Fig.  104. 

315.  A  simple  hydro- 
static balance  may  be  extemporized  by  replacing  one  of  the 
stirrups  of  an  ordinary  good  simple  lever  equal-armed  bal- 
ance by  another  and  much  shorter  stirrup,  soldering  a  hook 
to  the  bottom  of  the  pan  placed  on  that  short  stirrup,  and 
restoring  the  equipoise  by  using  enough  solder  to  effect  that 
result.  A  plummet  of  glass  is  then  suspended  by  a  platinum 


1.0460 


0.8642 


Fig.  104.  How  to  read  the  indications 
of  the  riders. 


158 


BALANCES,   HYDROMETERS,   PYCNOMETERS,   ETC. 


wire  to  the  hook  under  the  pan,  and  may  be  weighed  in  any  liquid, 
the  sum  of  the  weights  necessary  to  overcome  the  force  of  the 
buoyancy  being  the  weight  of  the  liquid  displaced.  The  weight 
of  the  water  displaced  by  the  plummet  may  be  determined  once 
for  all  and  recorded  or  engraved  upon  it,  and  if  that  weight  be  a 
simple  number  of  weight  units,  such  as  10  Gm  or  5  Gm,  the  di- 
vision of  the  weight  of  the  other  liquid  by  the  weight  of  the  same 
volume  of  water  is  extremely  simple. 

316.  When  solids  of  different  densities  are  mixed  with  each 
other  and  it  is  desired  to  separate  the  heavier  from  the  lighter 
this  separation  may  be  effected  by  adding  a  liquid  which  is  lighter 
than  the  heavier  solids  and  heavier  than  the  lighter  solids. 

317.  A  Pycnometer  is  a  bottle  constructed  so  that  it  can  be 

conveniently  used  for  the  determination  of 
the  densities  of  liquids.  Pycnometers  are 
often  called  "specific  gravity  bottles." 
Several  such  bottles  are  figured  here. 
The  bottle  should  be  made  to  hold  ex- 
actly 25  or  50  or  100  Gm  of  pure  water  at 
15°  C. ;  but  many  pycnometers  are  ad- 
justed to  the  temperature  of  15.° 5  instead 
of  15°.  The  best  pycnometers  are  cylin- 
drical rather  than  round,  of  light  weight 
(thin  glass),  provided  with  well  ground 
stoppers  with  vertical  capillary  tubes  bored 
through  their  centers.  Or  the  stopper  of 
the  pycnometer  may  be  a  thermometer, 
while  a  second  longer  neck  is  provided 
with  a  cap  or  a  perforated  ground  stop- 
per. The  instrument  may  be  accompanied  by  a  counterpoise. 

When  the  pycnometer  is  to  be  used  it  is  filled  to  the  brim  with 
the  liquid  to  be  tested,  and  the  stopper  or  stoppers  then  carefully 
but  firmly  inserted,  after  which  the  outside  of  the  instrument  is 
washed  with  water  or  alcohol  if  necessary  and  wiped  dry  with 
blotting  paper,  and  then  weighed  with  its  contents.  The  tare  or 
weight  of  the  Bottle  must  be  deducted  from  the  total  weight  if  a 
counterpoise  is  not  used.  The  temperature  at  which  the  opera- 
tion is  performed  is  to  be  observed  and  the  result  noted  and  used 
accordingly.  This  is  rendered  easy  when  a  thermometer  is  fitted 
into  the  bottle  as  a  stopper  to  it;  otherwise  the  temperature  of 


Fig.  105.  Plain  pycnometer 
with    counterpoise. 


BALANCES,    HYDROMETERS,   PYCNOMETERS,  ETC. 


159 


the  liquid  must  be  taken  by  a  thermometer  immersed  together 
with  the  filled  pycnometer  in  a  bath  and  allowed  to  remain  there 
until  of  the  desired  temperature  throughout  its  contents. 

318.  Adjustment  of  the  temperature.  It  is-  very  difficult  to  im- 
part to  any  liquid  the  precise  temperature  at  which  its  density 
is  to  be  found,  and  to  maintain  that  temperature  until  the  ob- 
servations are  completed.  A  bath  can  of  course  be  used  in 
which  water  is  cooled  with  the  aid  of  ice  until 
a  thermometer  inserted  in  the  liquid  indicates 
the  temperature  of  a  little  below  15°  C.,  after 
which  the  unmelted  portion  of  the  ice  may  be 
removed ;  but  the  temperature  of  the  water 
must  soon  rise  again  above  15°  if  the  tem- 
perature of  the  room  is  much  above  15.  It 
is,  therefore,  preferable  to  take  the  densities 
of  liquids  at  any  observed  temperature  near 
15°  C.,  and  to  make  corrections  afterwards 
for  the  contraction  caused  by  a  lower  tempera- 
ture or  the  expansion  caused  by  a  higher  tem- 
perature. 

When  pycnometers  with  thermometers  are 
used  the  bottle  may  be  filled  with  a  liquid 
having  a  temperature  a  little  below  15°,  and 
may  then  be  held"  in  the  hand,  with  filter  paper 
between  the  hand  and  the  bottle,  until  warmed 
to  15°.  Hydrometer  jars  containing  liquids 
may  be  warmed  in  the  same  manner ;  but  the 
hydrometer  itself  must  then  also  be  warmed 
at  the  same  time  so  that  the  process  is  here 
much  slower. 

319.  Tables  of  coefficients  which  must  be 
used  to  make    the  required    corrections    for 
deviations  from  the  standard  temperature  will 
be     found     in     special     works     on    weights, 
measures  and  specific  gravity,  and  in  other  books. 

320.  Graduated  flasks  are  quite  convenient  and  sufficiently  ac- 
curate for  ordinary  determinations  of  density.     They  should  be 
thin    flasks,   of   globe-shaped    or   pear-shaped   bodies   with    long 
slender  necks,  and  so  constructed  as  to  hold  50,  or  100,  or  200,  or 


Fig.  106.  Pycnometer 
with  thermometer. 


i6o 


BALANCES,    HYDROMETERS,   PYCNOMETERS,   ETC. 


500,  or  1,000  Grams  of  distilled  water  at  15°  C.  when  filled  to  the 
graduation  mark  etched  upon  and  around  the  neck. 

Such  flasks  are  often  marked  with  an  etched  inscription  stating 
their  capacity  in  Cc.  at  15.°;  but  they  are,  of  course,  graduated 
by  weight,  the  weight  does  not  change  with  variations  of  tem- 


Pig.  107.  Dr.  Squibb's  pycnometers. 


perature,  a  cubic-centimeter  is  a  Cc.  at  any  temperature,  and  the 
cubical  expansion  or  contraction  of  the  glass  flask  itself  is  not 
considered. 

To  find  approximately  the  density  of  any  liquid,  weigh  it  in  the 
graduated  flask,  and  divide  by  the  weight  of  the  same  volume  of 
water. 


BALANCES,    HYDROMETERS,   PYCNOMETERS,   ETC.  l6l 

321.  Hydrometers.  A  floating  body  displaces  its  own  weight 
of  the  liquid  in  which  it  floats — no  more,  and  no  less.  Hence  it 
sinks  deeper  in  lighter  liquids,  and  to  a  less  depth  in  heavier 
liquids.  Hydrometers  are  cylindrical  floats  so  constructed  that 
the  center  of  gravity  is  at  one  end,  with  an  expanded  part  of  the 
tube  just  above  the  loaded  bulb  which  fixes  the  center  of  gravity, 
the  object  of  the  expansion  being  to  keep  the  instrument  in  an 
upright  position  when  floating  in  a  liquid.  Several  forms  of 
hydrometers  are  represented  by  the  illustrations. 

Hydrometers,  or  areometers,  are  much  used  in  laboratories. 
The  most  useful  and  common  forms,  only,  will  be  referred  to  here. 

A  hydrometer  which  is  heavier  than  its  own  volume  of  the 
liquid  in  which  it  is  placed  would,  of  course,  sink  below  the  sur- 
face of  that  liquid  if  its  depth  is  sufficient ;  and  a  hydrometer  not 
sufficiently  heavy,  or  not  properly  con- 
structed, would  not  sink  down  far  enough  to 
assume  a  vertical  position.  But  a  hydrom- 
eter so  constructed  as  to  sink  down  to  about 
the  middle  in  water  might  be  used  for  liquids 
heavier  than  water  as  well  as  for  liquids 
lighter  than  water.  In  order,  however,  to 
render  the  hydrometer  convenient  as  well 
as  accurate,  each  instrument  is  made  to  indi- 
cate only  a  limited  range  of  densities,  and  Fig'  m  Graduated  flasks- 
the  tube  above  the  expanded  part  which  helps  to  constitute  the 
instrument  an  upright  float  is  made  sufficiently  long  to  render  the 
divisions  on  the  graduated  scale  large  and  distinct  enough  to  be 
easily  read  but  not  so  long  as  to  make  the  hydrometer  unwieldy. 

322.  The  two  most  common  hydrometers  are :   one  for  densi- 
ties ranging  from  i.ooo  up  to  1.300;  and  the  other  for  densities 
ranging  from  i.ooo  down  to  0.700.     The  first-mentioned  is  far 
more  commonly  used  than  any  other,  because  liquids  heavier  than 
water  but  not  heavier  than  1.300  sp.  gr.  are  the  most  common 
liquids  to  be  tested — salt  solutions,  etc.     A  hydrometer  for  liquids 
between  1.300  and  1.600  sp.  gr.  is  also  made,  and  another  for 
liquids  ranging  from  1.600  to  2.000;  but  these  are  rarely  used. 

The  four  hydrometers  just  described  are  called  "direct  specific 
gravity  hydrometers"  because  the  scales  within  or  upon  their 
slender  tubes  are  graduated  to  indicate  actual  densities. 

323.  Very  good  hydrometers  are  rarely  accurate  to  within 

Vol.    11—11 


162 


BALANCES,   HYDROMETERS,   PYCNOMETERS,   ETC. 


0.002  sp.  gr.,  and  many  instruments  fail  to  indicate  less  differences 
than  o.oio.  Hydrometers  are  therefore  much  less  reliable  than 
the  Mohr-Westphal  balance,  the  pycnometer,  or  the  graduated 
narrow-necked  specific  gravity  flask  (Par.  320);  but  their  con- 


Figs.  109  and  110.  Hydrometers. 


venience  is  so  great  that  hydrometers  are  largely  employed  when- 
ever approximately  correct  results  are  sufficient.  Hydrometers 
indicating  differences  of  0.005  may  be  regarded  as  extremely 


BALANCES,   HYDROMETERS,   PYCNOMETERS,  ETC. 


i63 


satisfactory  for  all  ordinary  laboratory  operations  in  the  manu- 
facture of  chemical  products. 

The  spaces  between  the  graduation  marks  on  the  hydrometer 
scales  are  always  larger  at  the  top  than  lower  down. 

324.  The  hydrometer  jar  (Fig.  no)  must  be  sufficiently  roomy 
to  allow  the  hydrometer  to  float  freely  without  coming  in  contact 
with  the  sides,  and  tall  enough  to  leave  the  upper  end  of  the 
hydrometer  protruding  above  the  top  of  the  jar  when  the  instru- 
ment is  immersed  in  the  lightest  liquid,  the 

density  of  which  is  included  within  the  range 
of  the  scale. 

325.  If  it  is  desired  to  take  observations 
of  density  at  15°  the  hydrometer  and  jar  must 
both  be  cooled  with  cold  water  before  they  are 
used. 

The  best  hydrometers  include  thermometers 
within  their  tubes  so  that  the  temperature  can 
be  observed  concurrently  with  reading  off  the 
density. 

326.  The  meniscus  renders  the  reading  dif- 
ficult, but  care  and  experience  will  enable  the 
operator  to   obtain   satisfactory   results;    the 
density  mark  at  the  middle  of  the  depth  of  the 
meniscus  indicates  the  correct  specific  gravity. 

327.  Large  hydrometers  demand  the  use 
of  much  liquid,  and  smaller  hydrometers  (each 

made  for  a  more  limited  range  of  densities)  are  accordingly  often 
preferred,  or  even  necessary. 

328.  Twaddell's  hydrometers  are  comparatively  small,  as  the 
graduated  scales  of  these  hydrometers  occupy  a  space  only  about 
75  millimeters  long.     They  are  made  in  sets  of  six,  and  as  the 
whole  range  of  densities  divided  up  between  these  six  instruments 
extends  only  from  o'to  174  degrees  or  from  the  sp.  gr.  i  to  1.870 
the  degree  spaces  are  large  enough  to  be  easily  read.    The  zero 
on  Twaddell's  scale  corresponds  to  the  density  of  water  at  I5.°6  C. 
(60°  F.),  and  each  degree  above  the  o  represents  an  increase  of 
0.005  °f  tne  density  of  water,  so  that  2°  Twaddell  is  equivalent 
to  the  sp.  gr.  i.oi,  and  10°  Tw.  to  sp.  gr.  1.05. 

It  will  be  observed  that  Twaddell's  hydrometers  are  intended 
only  for  liquids  heavier  than  water. 


Fig.  111.  Rousseau's 
densimeter. 


164 


BALANCES,   HYDROMETERS,   PYCNOMETERS,   ETC. 


On  account  of  their  small  size  the  Twaddell  hydrometers  can  be 
used  in  the  customary  graduated  cylinders  of  100  Cc.  capacity, 
so  that  no  special  hydrometer  jar  is  necessary. 

To  convert  Twaddell  degrees  into  the  corresponding  specific 
gravity  multiply  the  number  of  degrees  by  0.005  and  add  I.  to 
the  product. 


o 
10- 

20- 
30- 
40" 

50- 
60- 
70 


70- 
60- 
50 
40 
30 
20 
10 
0 


Fig.  112.  Twaddell's  hydrometer. 


Fig.  113.    Baume's  hydrometers. 


329.  Baume's  hydrometers  were  once  very  generally  used ;  but 
are  falling  into  disuse  on  account  of  their  very  unscientific  scales 
of  degrees,  and  their  uncertain  standards. 

The  Baume  hydrometer  for  heavy  liquids  is  assumed  to  des- 
cend to  o  in  water  at  12° ,5  C,  and  to  descend  to  the  point  marked 
15°  in  a  solution  made  of  15  parts  of  sodium  chloride  in  85  parts 
of  water. 


BALANCES,   HYDROMETERS,  PYCNOMETERS,  ETC.  165 

The  Baume  hydrometer  for  light  liquids  is  assumed  to  sink 
to  o  in  a  10  per  cent  solution  of  sodium  chloride  at  12.°  5  C.  and 
to  10°  in  pure  water. 

The  Baume  hydrometer  should  be  altogether  discarded,  but  as 
"degrees  Baume"  are  referred  to  in  many  valuable  old  works 
the  following  rules  for  converting  Baume  degrees  to  sp.  gr.  and 
vice  versa  are  here  given.  These  rules  refer  to  Baume  scales 
used  in  the  United  States  and  hold  good  at  the  temperature  of 
i5.°6  C.  (60°  R). 


Fig.  114.  Graduated  cylinders. 


For  liquids  heavier  than  water. 

I.  To  convert  Baume  degrees  into  specific  weight,  divide 
145  by  the  remainder  obtained  by  deducting  the  number  of 
Baume  degrees  from  145 : 


145 


sp.  w. 


i45-B° 

II.     To  convert  specific  weight  into  the  corresponding  degrees 


l66  BALANCES,    HYDROMETERS,   PYCNOMETERS,   ETC. 

Baume,  subtract  from  145  the  quotient  obtained  by  dividing  145 
by  the  specific  weight : 

H5 

145  =     B°. 

sp.  w. 

For  liquids  heavier  than  water. 

III.     To  convert  Baume  degrees  into  specific  weight,  divide 
140  by  the  sum  of  130  plus  the  number  of  degrees: 

140 

=     sp.  w. 


i3o+B° 

IV.  To  convert  specific  weight  into  the  corresponding  number 
of  degrees  Baume,  divide  140  by  the  specific  weight  and  from  the 
quotient  subtract  130: 

'  140 
_     130    =     B°. 


sp.w. 

330.  The  knowledge  of  the  density  of  a  substance  aids  in  its 
identification,  and  in  the  determination  of  its  purity  and  strength, 
and  enables  us  to  compute  the  weight  from  the  volume  and  the 
volume  from  the  weight.    It  is  also  a  guide  in  the  concentration  of 
solutions  by  evaporation  for  various  purposes. 

331.  Specific  volume.*    The  specific  volume  of  a  liquid  is  the 
reciprocal  of  its  specific  weight. 

Its  utility  in  laboratory  work  is  great. 

To  convert  any  number  of  grams  into  the  corresponding  num- 
ber of  milliliters,  or  any  number  of  kilograms  into  the  correspond- 
ing number  of  liters,  multiply  by  the  specific  volume. 


*The  term  specific  volume  and  its  employment  were  proposed  by 
the  author  of  this  book  in  1883,  in  a  paper  read  before  the  American 
Pharmaceutical  Association.  See  Proceedings  of  that  Association  for  the 
year  named. 


CHAPTER  XVIII. 

RULES   FOR   MAKING     SOLUTIONS     AND     MIXTURES    OF    ANY     GIVEN 
STRENGTH,  AND  FOR  DILUTING,   FORTIFYING  AND   MIXING. 

332.  To  make  solutions  and  mixtures  of  any  given  percent- 
age strength  all  the  quantities  and  values  employed  should  refer 
to  weight. 

Accurate  results  are  obtained  when  all  the  materials  are  meas- 
ured by  weight,  because  mass  is  not  affected  by  contraction  or 
expansion  of  volume. 

But  when  the  quantities  of  the  materials  or  ingredients  are 
measured  by  volume  instead  of  by  weight,  or  when  the  quantity 
of  one  of  two  ingredients  is  measured  by  weight  and  that  of  the 
other  by  volume,  the  exact  strength  of  the  mixture  or  solution 
can  not  be  directly  or  easily  computed  or  expressed. 

Even  if  the  mixture  or  solution  is  composed  of  two  liquids, 
their  proportions  should  be  stated  and  computed  by  weight  and 
not  by  volume,  because  the  volume  of  the  resulting  mixture  or 
solution  is  generally  less  than  the  sum  of  the  original  volumes  of 
the  two  component  liquids,  so  that  the  proportion  which  the  vol- 
ume of  either  of  these  two  liquids  bears  to  the  final  volume  of 
the  product  can  not  be  known  from  the  proportions  employed. 
A  mixture  of  alcohol  and  water,  one  hundred  volumes  of  which 
contain  fifty  volumes  of  absolute  alcohol,  contains  an  amount  of 
water  which  separately  must  measure  more  than  fifty  volumes. 
A  statement  of  percentage  strength  or  composition  referring  to 
volume  proportions  is  accordingly  unreliable  and  deceptive. 

Nevertheless  it  is  so  convenient  for  many  pharmaceutical  pur- 
poses to  prepare  solutions  and  liquid  mixtures  volumetrically,  or 
to  measure  the  solids  by  weight  and  the  liquids  by  measure  in 
making  preparations  composed  of  both,  that  it  is  a  common  prac- 
tice, and  the  results  are  in  most  cases  sufficiently  nearly  accurate 
for  those  purposes. 

When  absolute  exactness  is  necessary,  however,  all  quantities 
and  values  employed  in  working-formulas,  in  actual  work,  and  in 
statements  of  strength  referring  to  liquids  must  be  expressed  in 

167 


l68  RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES. 

terms  of  weight  exclusively.  Gravimetric  methods,  .formulas  and 
expressions  are  always  practicable  and  exact,  and  for  nearly  all 
purposes  in  chemical  laboratory  work  they  are  preferable  in  point 
of  convenience  as  well  as  scientific  accuracy. 

333.     The  following- 
Rule  for  computing  quantities  and  proportions  in  making  mix- 
tures and  solutions  will  be  found  applicable  in  most  cases : 

Having  a  known  quantity  (a)  of  one  ingredient  of  known  value 
(A),  and  desiring  to  find  the  quantity  (x)  of  the  second  ingredient 
of  known  value  (B)  which  will  be  required  to  produce  a  mixture 
of  any  intermediate  value  (c) — Multiply  the  known  quantity  of 
the  first  ingredient  (a)  by  the  difference  between  its  value  (A) 
and  the  desired  value  of  the  mixture  (c)  ;  divide  the  product  by 
the  difference  between  the  value  of  the  second  ingredient  (B) 
and  the  desired  value  of  the  mixture  (c).  The  quotient  is  the 
quantity  desired  of  the  second  ingredient  (x). 

For  the  purposes  of  the  foregoing  rule  the  term  "ingredient" 
applies  to  each  of  the  two  components  of  any  mixture  or  solu- 
tion. Thus  the  two  ingredients  of  any  solution  are  the  solvent 
and  the  dissolved  substance ;  the  ingredients  of  any  dilute  alcohol 
are  the  alcohol  and  water ;  and  the  components  of  any  mixture  of 
two  solutions  of  different  strength,  or  of  a  mixture  of  a  stronger 
and  a  weaker  alcohol,  or  of  a  mixture  of  a  stronger  and  a  weaker 
opium,  are  also  designated  as  "ingredients." 

The  "value"  of  each  ingredient  as  well  as  the  value  of  the 
mixture  must  be  expressed  in  per  cent  by  weight. 

If  the  "ingredients"  are  water  and  potassium  bromide,  then  the 
value  of  the  water  is  o  and  the  value  of  the  bromide  100;  in  a 
mixture  of  absolute  alcohol  and  water,  the  alcohol  has  a  value  of 
100  and  water  o.  If  opium  is  one  ingredient  and  milk  sugar  the 
other,  the  value  of  the  opium  may  be  expressed  as  100  and  that 
of  the  mik  sugar  as  o  if  the  value  of  the  mixture  is  to  be  expressed 
in  terms  per  cent  of  opium;  but  if  the  value  of  the  opium  be 
expressed  in  per  cent  of  morphine,  then  the  strength  of  the  milk 
sugar  and  of  the  mixture  must  also  be  expressed  in  the  same 
terms.  Thus  if  an  opium  containing  16  per  cent  of  morphine  is 


RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES.  169 

to  be  diluted  with  milk  sugar  to  14  per  cent,  then  the  value  of  the 
opium  in  this  case  must  be  16  and  that  of  the  milk  sugar  o. 

If  a  mixture  is  to  be  made  of  alcohol  and  glycerin,  to  contain  a 
definite  per  cent  of  alcohol  by  weight,  then  the  value  of  the 
alcohol  for  the  purposes  of  the  application  of  our  rule  will  be 
100  and  that  of  the  glycerin  o  ;  but  if  the  value  of  the  mixture  is 
to  be  expressed  according  to  the  per  cent  of  glycerin  it  contains, 
then  the  value  of  the  alcohol  will  be  expressed  by  o  and  that  of 
the  glycerin  by  100. 

If  a  mixture  is  to  be  made  of  any  two  ingredients  of  unequal 
value,  the  rule  is  still  applicable.  It  thus  applies  to  the  dilution 
or  fortification  of  all  solutions  and  mixtures  in  which  two  in- 
gredients, one  weaker  and  one  stronger,  are  employed  as  the 
ingredients  or  components. 

The  term  "mixture"  includes,  for  the  purposes  of  this  rule,  all 
solutions. 

If  we  designate  as  (d)  the  difference  between  the  value  of  the 
first  ingredient  (A)  and  the  value  sought  (c),  and  as  (D)  the  dif- 
ference between  the  value  of  the  second  ingredient  (B)  and  the 
desired  value  of  the  mixture  (c),  the  rule  may  then  be  reduced  to 
the  following  algebraic  formula  — 


It  makes  no  difference  which  of  the  two  ingredients  is  desig- 
nated as  "first"  or  "second." 

Examples. 

i.  How  shall  a  30  per  cent  solution  be  made  of  potassium 
hydroxide  and  water? 

The  value  of  the  first  ingredient,  KOH,  is  100,  and  the  differ- 
ence between  100  and  30  is  70. 

The  value  of  the  second  ingredient,  the  water,  is  o,  and  the  dif- 
ference between  o  and  30  is  30. 

Designating  the  quantity  of  potassium  hydroxide  as  I,  the  ap- 
plication of  the  rule  would  give  — 

1X70 

---  =2.333=the  number  of  weight  units  of  water  to  be 

30 
added  to  each  weight  unit  of  potassium  hydroxide. 


I7O  RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES. 

2.  How  much  water  must  be  added  to  30  Gm  of  potassium 
hydroxide  to  make  a  30  per  cent  solution  of  it  ? 

(loo— 3o)X30 

=70. 

30—0 

Answer:     70  Gm  of  water. 

3.  How  much  zinc  sulphate  must  be  added  to  200  Gm  of  water 
to  produce  a  solution  of  4  per  cent  strength  ? 

The  water  may  be  called  the  first  ingredient  and  has  a  value 
of  o.  The  zinc  sulphate  is  the  second  ingredient  and  its  value  is 
100.  Then— 

2ooX(4— o) 

-  =8.333  Gm. 
100 — 4 

Answer:     8.333  Gm  of  zinc  sulphate. 

4.  How  much  solution  of  3  per  cent  strength  can  be  made  out 
of  400  Gm  of  a  solution  of  18  per  cent  strength? 

Let  us  find  how  much  water  must  be  added. 

4ooX(i8— 3) 
=2000  Gm. 


Answer :  2000  Gm  of  water  must  be  added  to  the  400  Gm  of 
1 8  per  cent  solution,  producing,  therefore,  2400  Gm  of  3  per  cent 
solution. 

5.  How  much  solution  of  50  per  cent  strength  must  be  added 
t°  333-33  Gm  of  water  to  produce  a  solution  of  30  per  cent 
strength  ? 

333-33  X  (30—0) 
=500  Gm. 

50—30 

Answer:  500  Gm  of  50  per  cent  solution  must  be  added  to 
333-33  Gm  of  water  to  produce  833.33  Gm  of  solution  of  30  per 
cent  strength. 

6.  How  much  zinc  sulphate  must  be  added  to  600  Gm  of  a  20 
per  cent  solution  of  that  salt  to  increase  the  strength  of  the  solu- 
tion to  25  per  cent  ? 


RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES. 

25  —  20) 

--  =40  Gm. 


100  —  25 

Answer  :  40  Gm  of  zinc  sulphate  added  to  600  Gm  of  a  20  per 
cent  solution  of  zinc  sulphate  will  make  640  Gm  of  a  solution  of 
25  per  cent  strength. 

7.  How  much  of  a  borax  solution  of  5  per  cent  strength  must 
be  added  to  800  Gm  of  a  borax  solution  of  2  per  cent  strength  to 
produce  a  solution  of  3  per  cent  strength? 

8ooX(3—  2) 

--  400  Gm. 

5—3 

Answer:  400  Gm  of  borax  solution  of  5  per  cent  strength 
added  to  800  Gm  of  a  solution  of  2  per  cent  strength  will  produce 
1  200  Gm  of  borax  solution  of  3  per  cent  strength. 

8.  How  much  alcohol  of  91  per  cent  must  be  added  to  3000 
Gm  of  alcohol  of  41  per  cent  strength  to  produce  a  mixture  con- 
taining 75  per  cent  of  alcohol? 

300oX(75—  40 

-  =6375  Gm- 
91—  75 

Answer:  6375  Gm  of  alcohol  of  91  per  cent  strength  mixed 
with  with  3000  Gm  of  alcohol  of  41  per  cent  will  make  9375  Gm 
of  an  alcohol  of  75  per  cent. 

9.  How  much  alcohol  of  41  per  cent  strength  must  be  added 
to  6375  Gm  of  alcohol  of  91  per  cent  strength  to  produce  an  alco- 
hol of  75  per  cent  ? 

6375X(9i—  75) 

-  =3000  Gm. 

75—41 

10.  How  much  glycerin  must  be  added  to  864  Gm  of  alcohol 
to  produce  a  mixture  containing  10  per  cent  of  glycerin? 

864X(io—  o) 

—  =96  Gm. 
100  —  10 

Answer  :    96  Gm  of  glycerin. 


172  RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES. 

11.  How  much  glycerin  must  be  added  to  864  Gm  of  alcohol  to 
produce  a  mixture  containing  10  per  cent  of  alcohol? 

864X(ioo— 10) 

=7776  Gm. 

10 — o 

Answer :  7776  Gm  of  glycerin  added  to  864  Gm  of  alcohol  will 
produce  a  mixture  containing  10  per  cent  of  alcohol. 

12.  How  much  opium  containing  10  per  cent  of  morphine 
must  be  added  to  420  Gm  of  opium  containing  18  per  cent  of 
morphine  in  order  to  make  a  mixture  containing  13  per  cent  of 
morphine  ? 

420X(  18—13) 

=700  Gm. 

13—10 

Answer:  700  of  opium  of  10  per  cent  strength  and  420  Gm 
of  opium  of  18  per  cent  strength  when  mixed  will  make  1120  Gm 
of  opium  of  13  per  cent  morphine  strength. 

334.  To  find   the   relative  proportions   required  of  salt  and 
water  to  make  100  Gm  of  any  salt-solution  of  any  given  strength : 

Rule.  Subtract  the  desired  per  cent  from  100;  the  remainder 
will  show  the  number  of  Gm  of  water  required.  The  number 
expressing  the  desired  percentage  strength  of  the  solution  will  be 
the  number  of  Gm  of  salt  required. 

Ex.  To  make  100  grains  of  a  4  per  cent  solution  of  cocaine 
hydrochlorate  use  4  grains  of  cocaine  hydrochlorate  and  96  grains 
of  water. 

335.  To  find  the  quantity  of  salt  (a)  which  must  be  added 
to  any  given  quantity  of  water  (b)  to  produce  a  solution  of  any 
given  per  cent  strength   (c),  and  the  quantity  of  solution  ob- 
tained (d)  : 

Rule.  Multiply  the  grams  of  water  (b)  by  the  desired  per 
cent  of  the  solution  (c)  to  be  made,  and  divide  the  product  by 
the  remainder  found  by  subtracting  the  number  expressing  that 
per  cent  from  100 ;  the  quotient  will  be  the  number  of  grams  of 


RULES  FOR  MAKING  SOLUTIONS  AND  .MIXTURES  173 

salt  (a)  which  must  be  added  to  the  grains  of  water  (b).  The 
sit  in  of  the  number  of  grams  of  salt  and  water  is,  of  course,  the 
weight  of  the  solution  (d). 

Formula — 
bXc 


=a;  and  a-\-b=d. 


100 — c 

Explanation — 

(100 — c)  :  b=c  :  a;  and  a-\-b=d. 

Ex.  To  find  the  number  of  Gm  of  mercuric  chloride  required 
to  be  added  to  ten  kilograms  of  water  to  make  a  o.i  per  cent 
solution,  multiply  10,000  by  o.i,  and  divide  the  product  (100,000) 
by  100 — o.i  (or  99.9).  The  quotient  is  100.1  Gm,  which  is  the 
quantity  of  mercuric  chloride  required. 

336.  To  find  the  kilos  of  water  (b)  required  for  any  given 
number  of  kilos  of  salt  (a)  to  make  a  solution  of  any  given  per- 
centage (c)  strength,  and  the  kilos  of  solution  produced  ( d)  : 

Rule.  Multiply  the  kilos  of  salt  (a)  by  100,  and  divide  the 
product  by  the  desired  percentage  strength  (c)  of  the  solution 
to  be  made.  The  quotient  is  the  number  of  kilos  of  solution  (d) 
which  will  be  produced  by  the  salt;  and  the  difference  betiveen 
the  kilos  of  salt  (a)  and  the  kilos  of  solution  formed  (d)  will 
be  the  kilos  of  water  required  (b). 

Formula — 
aXioo 

c 

Explanation — 
c  :  0=100  :  d;  and  cXd=aXioo. 

Ex.  In  making  an  8  per  cent  solution  out  of  24  kilograms  of 
sodium  carbonate,  how  much  solution  will  be  obtained  and  how 
much  water  must  be  used? 


174  RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES. 

24X100 

=300 ;  and  300 — 24=276. 

8 

Answer :  300  kilograms  of  8  per  cent  solution  will  be  produced 
out  of  24  kilograms  of  sodium  carbonate  and  276  kilograms  of 
water. 

337.  To  find  the  quantity  of  weaker  solution  of  any  given 
strength  that  can  be  .made  out  of  any  given  quantity  of  a  stronger 
solution,  and  thus  also  the  quantity  of  diluent  required: 

Rule.  Multiply  the  grams  of  the  stronger  solution  (a)  by  its 
percentage  strength  (b),  and  divide  the  product  by  the  desired 
lower  percentage  strength  (c)  ;  the  quotient  is  the  grams  of 
weaker  solution  (d)  produced  by  the  stronger  solution  (a).  The 
difference  between  d  and  a  is  the  number  of  grams  of  diluent  re- 
quired (e). 

Formula — 


Explanation  — 

c  :  b=a  :  d;  and  cXd= 


Ex.  If  200  Gm  of  a  solution  of  50  per  cent  is  to  be  diluted  to 
30  per  cent  — 

200X50 

"  =333-33  ;  and  333-33—200=133.33. 
30 

Answer:  333.33  Gm  of  the  30  per  cent  solution  can  be  made 
from  200  Gm  of  50%  solution,  so  that  the  quantity  of  water  to 
be  added  is  133.33  Gm. 

338.  To  find  the  quantity  of  stronger  solution  required  to 
make  any  given  quantity  of  weaker  solution,  and  thus  also  the 
quantity  of  diluent  required  : 


RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES.  175 

Rule.  Multiply  the  required  quantity  of  the  weaker  solution 
(a)  by  its  desired  per  cent  strength  (b),  and  divide  the  product 
by  the  percentage  strength  (c)  of  .the  stronger  solution;  the 
quotient  is  the  quantity  required  (d)  of  the  stronger  solution.  The 
quantity  of  diluent  required  (e)  is  the  difference  between  a  and  d. 

Formula — 


Explanation  — 

c  :b—a  :f;  and  cXd= 


Ex.  How  much  25  per  cent  solution  will  be  required  to  make 
600  Gm  of  a  20  per  cent  solution  ?  And  how  much  water  ? 

600X20 

--  =480  ;  and  600  —  480=120. 

25 

Answer:  480  Gm  of  25%  solution  and  120  Gm  of  water  will 
make  600  Gm  of  20%  solution. 

339.  To  find  the  kilos  of  water  (.#•)  required  to  be  added  to 
each  kilo  of  a  solution  of  any  given  percentage  strength  to  dilute 
it  to  any  less  percentage  desired  : 

Rule.  Divide  the  percentage  strength  (a)  of  the  stronger 
solution  by  the  percentage  desired  (b),  and  subtract  i  from  the 
quotient. 

Formula  — 


Ex.     A  90%  solution  is  to  be  diluted  to  60%.    How  many  kilos 
of  water  must  be  added  to  each  kilo  of  the  90%  solution? 


176  RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES, 

90 

—  =1.50;  and  1.50 — 1=0.50. 
60 

Answer :  0.50  kilo  of  water  must  be  added  to  each  kilo  of  the 
90  per  cent  solution. 

340.  To  find  the  absolute  quantities  of  salt  (a)  and  water  (b) 
required  to  make  any  given  quantity  of  solution  (c)  of  any  given 
strength  (d). : 

Rule.  Multiply  the  grams  of  solution  required  (c)  by  the  de- 
sired percentage  strength  (d),  and  divide  the  product  by  ioo. 
The  quotient  is  the  grams  of  salt  required  (a).  The  grams  of 
water  (b)  required  is  the  difference  between  the  grams  of  salt  (a) 
and  the  grams  of  solution  (c). 

Formula — 

=a;  and  c — a=b. 

ioo 

Explanation — 

ioo  :  d=c  :  a;  and  iooXo=^Xd. 

Ex.  How  much  sodium  hydroxide  is  required  to  make  500 
Gm  of  a  6%  solution?  And  how  much  water? 

500X6 

-  =30 ;  and  500—30=470. 
ioo 

Answer :    30  Gm  of  sodium  hydroxide  and  470  Gm  of  water. 

341.  To  find  the  percentage  strength  of  any  salt-solution  from 
the  grams  of  salt  contained  in  a  given  number  of  grams  of  solu- 
tion : 

Rule.  Multiply  the  grams  of  the  salt  (a)  fry  ioo  and  divide 
by  the  grams  of  the  solution  (b)  ;  the  quotient  is  the  percentage 
(c). 


RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES.  177 

Formula — 


b 

Explanation — 

b  :  ioo=a  :  c;  and   b~)(c= 


Ex.  If  2.25  Gm  of  absolute  acetic  acid  be  contained  in  50  Gm 
of  a  water  solution  of  it,  the  percentage  strength  of  the  solution 
must  be  4.50%,  for— 

2.25X100 

-  =4-50. 
50 

342.  To  find  the  percentage  strength  (a)  of  a  solution  from 
the  weight  of  the  solvent  (b)  and  of  the  solution  (c)  : 

Rule.  Subtract  the  weight  of  the  solvent  (b)  from  the  weight 
of  the  solution  (c)  ;  multiply  the  remainder  by  100,  and  divide 
the  product  by  the  zveight  of  the  solution  (c).  The  quotient  is 
the  percentage  (a). 

Formula — 
(c— 6)Xioo 


Explanation — 

(c — b)  :  c=a  :  100;  and  cXa=(c — &)Xioo. 

Ex.  If  1000  Gm  of  water  be  saturated  with  a  salt  and  the  total 
weight  of  the  solution  formed  be  found  to  be  1100  Gm,  what  is 
the  percentage  strength  of  the  solution? 

( i 100 — 1000) X 100 

=9.0909. 

IIOO 

Answer  :    9.09  per  cent. 

Vol.    11-12 


1/8  RULES  FOR  MAKING  SOLUTIONS  AND  MIXTURES. 

334.  Alligation  is  frequently  a  convenient  method  of  finding 
the  proportions  required  of  two  or  more  ingredients  of  different 
values  required  to  produce  a  mixture  of  any  value  intermediate 
between  the  highest  and  lowest. 

To  find  the  proportions  required  of  any  two  ingredients  of  dif- 
ferent values  required  to  produce  a  mixture  of  any  desired  inter- 
mediate value. 

Rule.  The  number  of  parts  required  of  the  weaker  ingredient 
(a)  is*the  difference  between  the  -value  (percentage  strength)  of 
the  stronger  ingredient  (b)  and  the  desired  value  of  the  mix- 
ture (c). 

The  number  of  parts  required  of  the  stronger  ingredient  (d) 
is  the  difference  between  the  desired  value  (percentage  strength) 
of  the  mixture  (c)  and  the  value  of  the  weaker  ingredient  (e). 

a=b — c  and  d=c — e. 

Ex.  To  make  a  mixture  of  7  per  cent  strength  out  of  one  of  3 
per  cent  and  another  of  12  per  cent,  use  12 — 7=5  parts  of  the 
3  per  cent  ingredient  and  7 — 3=4  parts  of  the  12  per  cent  ingre- 
dient. 


CHAPTER  XIX. 

FURNITURE  AND  APPARATUS. 

335.  The  outfit  of  apparatus  for  a  pharmaceutical  laboratory 
in  which  chemical  preparations  are  made  must  vary  to  so  great  an 
extent  according  to  the  quantity  and  variety  of  the  products,  and 
according  to  other  circumstances,  that  a  definite  description  of 
such  a  laboratory  is  scarcely  practicable.    A  few  general  sugges- 
tions may,  however,  be  found  useful  to  pharmacists  as  well  as 
students  who  desire  to  undertake  to  make  chemical  preparations. 

Certain  laboratory  furniture,  fixtures  and  apparatus  are,  of 
course,  always  necessary. 

These  include  wall  fixtures,  such  as  shelving,  cupboards,  a  case 
of  drawers,  good  water-supply,  one  or  more  sinks,  good  ventila- 
tion, one  or  more  effective  flues  with  which  to  connect  a  drying 
closet  and  a  hood  or  fume  chamber,  work  tables,  heating  appara- 
tus, a  good  still  for  making  distilled  water,  a  press,  and  a  suffi- 
cient outfit  of  pots  and  pans,  jars,  bottles,  strainer  frames  and 
stands,  dishes,  funnels,  filter  stands,  glassware,  etc. 

FURNITURE  AND  FIXTURES. 

336.  If  the  products  made  include  considerable  quantities  of 
precipitates  and  crystallized    salts  requiring    drying,    a    drying 
closet  is  of  great  advantage.     In  large  laboratories  two  or  more 
drying  closets  kept  at  different  temperatures  are  more  serviceable 
than  one  large  one;  or  a  special  drying  room  and  one  or  two 
closets  are  used.    Small  drying  closets  may  be  heated  by  means  of 
steam  coils,  hot  water  coils,  or  hot  air,  according  to  circumstances'. 
Where  steam  or  hot  water  can  not  be  had  the  drying  closet  may 
be  heated  by  means  of  a  suitable  gas  burner  or  gas  stove,  or  by 
a  gasoline  or  oil  burner,  placed  at  the  bottom.    The  closet  must, 
of  course,  be  provided  with  openings  to  admit  air  below  the  heat- 
ing appliance  used,  and  also  at  the  top  so  that  a  current  is  estab- 
lished.   The  top  of  the  closet  should  be  connected  with  an  effec- 
tive flue,  if  possible ;  but  if  this  can  not  be  done  some  other  means 
of  establishing  a  draft  should  be  adopted.     The  current  of  air 

179 


l8o  FURNITURE  AND  APPARATUS. 

passing  through  the  drying  closet  need  not  (and,  for  most  pur- 
poses, should  not)  be  strong.  Racks  for  shelves  or  frames  are 
so  arranged  that  the  circulation  of  air  is  not  impeded.  For  some 
purposes  it  is  admissible  to  use  shelves  made  of  galvanized  iron 
wire  grating.  Strips  of  plate  glass,  wood,  or  tinned  iron  are  often 
employed  instead  of  shelves. 

The  moist  products  to  be  dried  in  the  drying  closet  are  spread 
out  upon  filter  paper  or  muslin  placed  on  the  shelves  or  strips. 
It  is  important  to  regulate  the  temperature  well  so  that  substances 
liable  to  injury  from  too  high  heat  may  not  be  spoiled. 

337.  A  tight  fume  chamber  or  hood  connected  with  a  flue  hav- 
ing a  good  draft  is  essential  if  operations  are  to  be  performed 
resulting  in  the  evolution  of  irritating  or  poisonous  gases,  such 
as  nitrous  vapors,  chlorine,  sulphur  dioxide,  etc.    The  fume  cham- 
ber should  have  a  soapstone  bottom,  and  at  least  two  sides  of  it 
should  consist  of  movable  sash  with  double  thick  window  glass. 

338.  The  work  tables  must  be  strong  and  heavy.    They  should 
be  about  0.9  meter  high  and  not  over  0.6  meter  wide  if  placed 
lengthwise  against  the  wall,  but  about  I  meter  wide  if  out  from 
the  wall. 

One  of  the  tables  should  have  a  tin  covered  top  inclined  to- 
ward and  adjoining  the  sink,  and  this  table  should  be  exclusively 
for  apparatus  just  cleaned  and  left  to  be  drained. 

Another  table  adjoining  the  sink  should  be  covered  with  sheet 
lead  and  should  have  a  raised  edge  (also  covered)  all  around  it 
so  that  operations  in  which  corrosive  or  inflammable  liquids  are 
used  may  be  performed  more  safely. 

Soapstone  tables  are  most  desirable  for  operations  requiring 
the  continuous  use  of  powerful  burners. 

Other  work  tables  or  counters  should  have  wooden  tops. 

339.  If  practicable  there  should  be  in  any  large  laboratory  a 
specially  planned  place  for  stills,  pans,  strainer  stands  and  the 
press — a  place  where  the  floor  is  covered  with  asphalt  and  inclined 
toward  a  drain  so  that  the  water  which  is  frequently  freely  used 
in  connection  with  that  kind  of  apparatus  will  readily  run  off. 
If  an  asphalt  floor  is  impracticable  a  tin-covered,  low,  inclined 
platform  with  raised  edges  is  useful.    A  plentiful  and  convenient 
supply  of  water  with  taps  or  faucets  wherever  required  is  very 
important  here. 


FURNITURE  AND  APPARATUS.  l8l 

The  waste-pipes  from  steam  kettles,  stills,  etc.,  are  to  be  con- 
nected with  an  ample  outlet. 

BALANCES,  ETC. 

340.  A  special  room  or  place  for  the  balances  is  necessary  in 
all  large  laboratories.  In  a  pharmacy  where  the  laboratory  con- 
sists of  a  work-room  adjoining  the  officine,  all  weighing  and  meas- 
uring may  conveniently  be  done  with  the  same  instruments  that 
are  used  for  other  work.  In  large  manufacturing  laboratories  the 
materials  required  by  the  laborants  are  supplied  from  a  general 
store-room  upon  special  orders,  and  the  analytical  work  is  done 
in  another  room  specially  equipped  for  that  purpose. 

A  well-furnished  pharmaceutical  establishment,  even  if  very 
little  manufacturing  is  done  in  it,  should  have  several  balances. 
Balances  are  now  made  in  the  United  States  which  are  in  no  wise 
surpassed  by  any  foreign  made  instruments  of  the  same  kind. 

The  most  suitable  balances  for  a  well  ordered  pharmaceutical 
establishment  are: 

1.  An  analytical  balance  upon  which  quantities  ranging  from 
I  milligram  to  50  grams  may  be  weighed.     When  not  loaded  this 
balance  should  be  sensitive  enough  to  respond  to  i  milligram  by 
a  2  millimeters'  deviation  of  the  point  of  the  needle  from  the 
center  of  the  dial ;  when  this  balance  is  loaded  to  the  extent  of  50 
grams  the  needle  point  should  deviate  2  millimeters  from  the 
center  of  the  dial  on  the  impulse  of  5  milligrams. 

2.  The  ordinary  prescription  balance  should  be  used  to  carry 
loads  of  from  5  milligrams  to  5  grams.    The  sensitiveness  of  this 
balance  should  be  such  that  when  the  pans  are  not  loaded  the 
needle  should  deviate  2  millimeters  from  the  center  of  the  dial 
under  the  impulse  of  5  milligrams ;  when  the  pans  are  loaded  with 
50  Gm  each  the  point  of  the  needle  should  deviate  2  mm  from  the 
center  on  the  impulse  of  20  milligrams. 

3.  The  gram  balance  should  be  designed  for  loads  of  from  i 
to  250  Gm.     Its  sensitiveness  should  be  such  that  when  the  pans 
are  not  loaded  the  impulse  of  20  milligrams  placed  on  one  pan 
should  be  sufficient  to  cause  the  needle  to  deviate  2  millimeters 
from  the  center  of  the  dial ;  and  when  the  pans  each  carry  a  load 
of  250  Gm,  the  addition  of  50  milligrams  to  the  load  on  one  pan 


l82  FURNITURE  AND  APPARATUS. 

should  cause  the  needle  to  deviate  the  same  distance  from  the 
center. 

4.  The  kilogram  balance  should  be  constructed  to  carry  loads 
of  from  5  to  2000  Gm,  and  its  sensitiveness  should  be  such  that 
the  needle  point  deviates  from  the  center  by  2  millimeters  on 
the  impulse  of  50  milligrams  when  the  pans  are  not  loaded  and  on 
the  impulse  of  200  milligrams  when  they  are  loaded  with  2000 
Gm  each. 

One  or  two  larger  balances  may  also  be  necessary. 

A  Mohr-Westphal  balance  is  of  great  value. 

All  balances  should  be  placed  on  solid  tables  where  they  will 
be  safe  against  jarring  and  injury,  and  must  be  kept  well  pro- 
tected against  dust.  They  should  be  kept  scrupulously  clean  and 
dry,  and  no  chemicals  should  be  permitted  to  come  in  contact  with 
them.  They  should  above  all  be  protected  against  corrosive  sub- 
stances. When  not  in  actual  use  they  must  be  at  perfect  rest, 
with  the  knife-edges  relieved  from  friction. 

The  weights  should  also  be  kept  clean  and  accurate. 

341.  Graduated  glass  measures,  commonly  called  "graduates," 
are   necessary    in    every   pharmaceutical     establishment.      They 
should  be  graduated  in  accordance  with  but  one  system;  those 
graduated  according  to  the  old  system  of  fluid  measure  on  one 
side  and  in  cubic-centimeters  on  the  other  side,,  should  never  be 
used  for  any  purpose  because  such  double  graduation  leads  to 
frequent  errors. 

The  metric  system  having  now  been  adopted  in  every  pharma- 
copoeia, the  world  over,  pharmacists  should  do  all  in  their  power 
to  shorten  the  time  required  to  complete  the  change  from  the 
old  to  the  new,  not  only  because  resistance  to  the  inevitable  is 
useless  but  because  they  will  certainly  find  the  new  system  far 
more  convenient. 

Graduated  cylinders,  flasks,  pipettes,  burettes,  an  accurate 
pycnometer,  and  a  set  of  reliable  hydrometers  are  required  for  the 
analytical  work  inseparable  from  the  work  of  producing  and  dis- 
pensing chemical  preparations.  (See  Chapter  XV.) 

HEATING    APPARATUS. 

342.  Much  can  be  done  with  the  stoves,  furnaces  and  burners 
constructed  for  use  with  gas  as  the  fuel.     Illustrated  descriptive 


FURNITURE  AND  APPARATUS. 


catalogues  of  such  heating  apparatus  are  freely  furnished  by  deal- 
ers and  manufacturers  so  that  any  one  may  learn  more  from 
them  than  can  be  presented  in  any  text-book.  Among  the  most 
efficient  gas  burners  are  the  "Fletcher  low  temperature  burner," 


Fig.  115.  Graduated  glass  measure. 


Fig.  116.  Fletcher  burner 
("low  temperature  burner"). 


which  affords  a  wide  range  of  temperatures  from  gentle  heat  up 
to  red  heat ;  it  is  so  constructed  that  it  can  be  attached  to  a  pipe 
from  a  bellows  when  a  very  high  heat  is  to  be  produced,  and  it 


Fig.  117.  Fletcher  radical  burner. 


is  so  effective  that  the  designation  "low  temperature  burner"  is 
an  unfortunate  one  since  it  emphasizes  one  of  its  merits — that  the 
heat  can  be  thoroughly  controlled  and  kept  very  lew  if  desired — 


1 84 


FURNITURE  AND  APPARATUS. 


at  the  expense  of  the  equally  valuable  feature  which  enables  the 
operator  to  apply  an  exceptionally  high  heat. 


Fig.  118.    The  Jewel  gas  heater. 


Fig.  119.  Foot  blower. 


Fig.  120.  Iron  retort  for  the  production  gases  in 
"the  dry  way"  and  for  other  processes  re- 
quiring very  high  heat. 


Fig.  121.  Triple  Bunsen  burner.  Fig.  122.  Bunsen  burner  with  cone. 

The  Fletcher  "radial  burner"  (made  by  Buffalo  Dental  Mfg. 
Co.)  and  the  "Jewel"  gas  stove  (made  by  Geo.  M.  Clark  &  Co., 
of  Chicago)  are  particularly  serviceable  for  heating  large  vessels. 


FURNITURE  AND  APPARATUS. 


A  foot-blower  or  bellows  is  frequently  useful. 

Bunsen  burners  are  made  in  great  variety,  and  two  or  more 


Fig.  123.  Seven-tubed  Bunsen  burner. 


Fig.  124.  Erlenmeyer's  burner. 


well-made  ones  are  necessary  in  any  pharmaceutical  laboratory, 
however  small. 

Bunsen  burners  are  so  constructed  that  a  mixture  of  gas  and 
air  in  proper  proportions  is  first 
produced  and  more  complete  and 
rapid  combustion  and  a  maximum 
temperature  are  secured  by  burning 
that  mixture. 

The  supply  of  gas  admitted 
through  the  tube  of  the  Bunsen 
burner  can  be  regulated  by  the  gas 
stopcock,  and  the  supply  of  air  by 
means  of  the  movable  collar  which 
is  provided  with  two  opposite  cir- 
cular openings  acting  as  a  valve 
which  may  be  partially  or  entirely 
closed  by  turning  the  collar  so  as 
to  place  it  in  the  required  position 
opposite  the  openings  in  the  lower 
outer  tube  of  the  burner,  immedi- 
ately below  the  top  of  the  gas  tip 
which  it  surrounds,  as  seen  in 
the  cut. 

343.     When  sufficient  air  is  supplied  in 


125.  Shows  the  construction  of 
the  Bunsen  burner. 


proportion  to  the  gas, 


l86  FURNITURE   AND   APPARATUS. 

the  flame  is  non-luminous  or  bluish,  because  the  combustion  is 
then  complete ;  but  when  the  supply  of  air  is  shut  off  the  flame  is 
luminous,  yellow  and  smoky.  When  the  current  of  gas  is  too 
low  in  proportion  to  the  air  admitted  it  frequently  happens  that 
the  gas  ignites  back,  the  flame  receding  down  into  the  tube  to  the 
pin  hole  orifice  of  the  gas  tip.  The  whole  tube  then  at  once  be- 
comes very  hot  so  that  .the  rubber  tube  attached  to  the  burner 
may  melt,  the  escaping  gas  then  becoming  ignited  and  a  destruc- 
tive fire  may  result.  It  is,  therefore,  dangerous  to  leave  a  Bun- 
sen  burner  in  operation  with  the  gas  turned  low.  Whenever  it  is 
found  that  the  flame  of  the  Bunsen  burner  has  receded  to  the 


Fig.  126.  Bunsen  burner  flames;  the  cuts  contrast  a  proper  flame 
with   that  resulting  when  the  gas  is  "lighted  back"  into  the 
tube. 

base  or  "lighted  back"  the  gas  should  be  immediately  shut  off, 
and  the  burner  allowed  to  cool  off  completely  before  it  is  again 
re-lighted;  it  may  be  cooled  off  quickly  by  letting  cold  water 
flow  upon  it. 

344.  In  cases  where  it  is  necessary  to  allow  a  Bunsen  burner 
to  remain  lighted  a  long  time  without  constant  attention,  it  should 
be  placed  on  a  fire-proof  table  and  the  gas  should  be  supplied 
to  it  not  by  means  of  rubber  tubing  but  through  a  piece  of  gas- 
pipe  directly  attached  to  the  burner. 

345.  The  introduction  of  a  diaphragm  of  fine  wire  netting  in 
the  tube,  just  below  the  top,  prevents  the  flame  from  "striking 
back,"  but  it  also  reduces  the  intensity  of  the  heat  of  the  flame. 


FURNITURE  AND  APPARATUS. 


i87 


The  mixture  of  gas  and  air  passing  through  the  wire  netting  is 
ignited  above  it.  Gas  burners  constructed  on  this  principle  can 
be  easily  obtained. 

Special  burners  are  made  for  use  with  acetylene  as  the  fuel, 
and  acetylene  burners  produce  a  much  higher  temperature  than 
gas  burners. 

346.  The  Roessler  gas  furnace  is  a  very  efficient  apparatus 
for  small  crucible  operations  where  extremely  high  temperatures 
are  necessary.  It  can  be  used  with  either  gas  or  acetylene. 

Its  construction  is  shown  in  the  accompanying  cut.     It  will 


Fig.  127.  Roessler  furnace. 

heat  a  crucible  about  twelve  centimeters  high  having  a  diameter 
of  seven  centimeters  at  the  top.  The  length  of  the  chimney  may 
be  extended  to  about  two  meters  and  to  insure  a  strong  draft 
through  it  a  second  burner  is  used  at  its  foot. 

347.  When  gas  is  not  available  gasoline  burners  may  be  ad- 
vantageously used,  and  in  many  cases  a  good  coal  stove  or  a 
charcoal  furnace  may  be  found  useful. 

Spirit  lamps  are  extremely  valuable  for  small  and  brief  opera- 


1 88 


FURNITURE  AND  APPARATUS. 


tions  where  a  perfectly  smokeless  flame  and  high  heat  are  de- 
sired. 

348.  In  the  use  of  Bunsen  burners  spirit  lamps  and  other  burn- 
ers which  afford  one  solid  vertical 
flame,  the  most  intense  heat  is  just 
below  the  middle  of  the  flame. 

349.  When  a  vertical  flame  is 
used  it  is  often  necessary  to  dis- 
tribute and  moderate  the  heat  by 
interposing  zvire-gause  or  asbestos- 
cloth  between  the  flame  and  the  ves- 
sel heated.  The  gauze  or  cloth  may 
sometimes  incidentally  serve  as  a 
support  for  flasks,  beakers  and 
other  vessels  to  which  the  heat  is 
I!;;,  applied.  But  wire  gauze  is  soon 
''burnt  out."  Asbestos  cloth  is 

Fig.  128.  Earthed  spirit  .amps.         much  tQ  be  preferred. 

350.     Sand-baths  are  frequently  useful  for  supporting  flasks, 
retorts  and  dishes  which  are  to  be  strongly  heated,  serving  to 


Fig.  129.  Showing    the    effect    of    the   interposition    of   wire    cloth; 
the  gas  may  be  lighted  either  above  or  below  the  wire  cloth. 

distribute  the  heat.  Shallow  sand-bath  dishes  are  used  for  the 
support  of  beakers  and  evaporating  dishes  and  also  flasks ;  deeper 
sand-bath  dishes  are  necessary  for  heating  retorts  which  must 


FURNITURE  AND  APPARATUS. 


I89 


sometimes  be  completely  covered  with  the  sand.  Two  forms  of 
sand-bath  dishes,  made  of  the  best  "Russia  iron"  are  shown  in 
the  cuts.  A  still  deeper  sand-bath  is  occasionally  required. 
Iron  pots  are  used  for  large  sand-baths. 

The  sand  used  for  the  sand-bath  should  be  clean,  hard  flint 
sand,  not  too  fine  but  free  from  gravel. 

The  interposition  of  the  sand-bath  between  the  flame  and  the 


Fig.  130.  Tripod  with  rings. 
For  use  with  burners. 


Fig.  131.  Support  for  use 
with  a  Bunsen  burner. 


vessel  distributes  the  heat  very  effectively ;  but  it  also  causes  con- 
siderable loss  of  heat  and  lowers  its  intensity. 

351.  Water-baths  are  round  vessels  of  copper,  or  of  heavy 
tinned  iron,  with  either  spherical  or  flat  bottoms.  Copper  vessels 
are  by  far  the  best  because,  if  made  of  moderately  heavy  sheet 


Fig.  132.  Shallow  sand-bath  dish  of 
Russia  iron. 


Fig.  133.  Deeper  sand-bath  dish  of 
Russia  iron. 


copper  and  given  reasonable  care,  they  last  for  many  years  of  con- 
stant use  and  because  copper  is  an  excellent  conductor  of  heat. 

Water-baths  are  indispensable  in  pharmaceutical  laboratories. 
One  or  two  sizes  are  required,  if  not  more.  For  general  use  in 
comparatively  small  operations  the  best  water-baths  are  those 
provided  with  sets  of  concentric  rings  to  fit  different  sizes  of 
dishes  or  flasks. 

Water-baths  without  rings  are  used  for  special  purposes. 

Water-baths  with  constant  level  are  very  convenient,  for  the 


190  FURNITURE   AND   APPARATUS. 

ordinary  water-bath  requires  watching  and  frequent  replenishing 
with  water  to  prevent  their  running  dry  or  too  low,  which  usually 
results  in  damage.  The  constant  level  water-bath  is  so  con- 
structed that  the  water  vapor  does  not  escape,  but  is  condensed 
and  runs  back  into  the  body  of  the  vessel.  The  bath  shown  in  Fig. 


Fig.  134.  Small  round-bottomed   copper      Fig.  135.  Small   flat-bottomed  water- 
water-bath,  bath. 


Fig.  136.  Water-bath  with  attachment  to  maintain  a  constant 
level  of  the  water. 

137  is,  as  seen,  differently  constructed.  Various  kinds  may  be 
found  described  in  the  catalogues  of  dealers  in  chemical  ap- 
paratus. 

The  water-bath  when  in  use  should  be  kept  from  one-half  to 
three-fourths  rilled  with  water,  and  the  vessel  placed  upon  it 
should  not  fit  so  tightly  that  there  is  no  escape  for  the  steam, 
for  the  pressure  may  then  become  so  great  as  to  throw  the  vessel 


FURNITURE  AND  APPARATUS.  19! 

off  the  bath  or  to  cause  a  sudden  outburst  of  steam  which  might 
do  injury. 

The  temperature  afforded  by  the  water-bath  when  well  man- 
aged may  be  made  to  range  all  the  way  from  the  ordinary 
room  temperature  up  to  about  95°  C. 

352.  Salt  solutions   (for  from   100°   to   160°),  glycerin   (up 
to  165°),  and  paraffin  (up  to  250°)  are  frequently  employed  in 
baths  instead  of  water  for  the  purpose  of  imparting  heat.     The 
temperatures    afforded    vary    according    to    the    boiling    points. 
When  temperatures  below  the  respective  boiling  points  of  these 
several  liquids  are  required  it  is  necessary  to  use  thermometers  in 
order  to  be  able  to  guard  against  a  higher  heat  than  that  desired. 
Thermometers  are  especially  necessary  in  water-baths  when  the 
temperature  must  not  be  permitted  to  exceed  a  given  degree.     At 
the  same  time  the  water-bath  may  then  be  placed  a  greater  or 
less  distance  above  the  flame,  and  the  flame  or  fire  may  be  regu- 
lated as  circumstances  require. 

353.  Hot  water  coils  may  be  advantageously  used  to  heat 
sand  or  water  in  large  sand- 
baths     or     water-baths     em- 
ployed in  the  practice  labora- 
tories of  technical  schools  for 

the  use  of  the  classes.  Such 
sand-baths  and  water-baths 
may  be  made  to  afford  a 
reasonably  uniform  tempera- 
ture anywhere  between  30° 
and  70°. 

354.  Hot     air     chambers, 
heated  with  steam  or  hot  wa- 
ter,  and   tightly   closed,   may 
be  employed  for  maintaining 
nearly   uniform   temperatures 
for    various    laboratory    pur- 

rpi  n  i  Fig.  137.  Instantaneous  water  heater. 

poses.    They  are  usually  made 

of  plate  glass  in  frames  of  wood,  and  the  temperature  of  the  air 

in  them  is  observed  by  means  of  thermometers. 

Hot  air  ovens  and  hot  water  ovens  of  copper  are  used  for  drying 
small  quantities  of  various  substances. 

355.  Steam  heat  is  invaluable  in  large  manufacturing  labora- 


192 


FURNITURE  AND  APPARATUS. 


tories.  Even  small  steam  boilers  of  very  simple  construction 
are  of  great  utility  in  moderately  equipped  pharmaceutical  labora- 
tories. Where  steam  power  is  used,  the  steam  also  furnishes  the 
heat  for  pans,  stills,  etc. 


Fig.  138.  Small  drying  oven  in  use. 


The  temperature  imparted  by  steam-heating  apparatus  may  be 
regulated  so  that  it  can  be  kept  within  narrow  limits  at  any 


Fig.  139.  Double-walled  copper  oven. 


Fig.  140.  Copper  drying  oven. 


point  within  the  extreme  range  of  from  a  few  degrees  above  the 
ordinary  room  temperatures  up  to  100°.  The  steam  used  may 
be  under  a  pressure  of  from  three  or  four  pounds  to  the  square 


FURNITURE  AND  APPARATUS.  IQ3 

inch  up  to  twenty-five  pounds  or  more.  For  some  special  pur- 
poses, as  in  the  fractional  distillation  of  hydrocarbons  on  a 
large  scale  (in  the  manufacture  of  gasoline,  benzin,  lamp  oil,  etc.) 
the  steam  is  conducted  by  means  of  iron  pipes  through  a  furnace 
fire  to  raise  its  temperature  to  a  very  high  degree  (even  to  a 
point  at  which  it  makes  red  hot  the  iron  pipe  through  which  it 
passes  after  leaving  the  furnace)  before  it  is  applied.  Steam  so 
treated  is  called  "superheated"  or  "dry  steam." 

Steam  heat  is  applied  in  three  different  ways:  i,  by  means 
of  coils ;  2,  by  means  of  jackets ;  and  3,  by  conducting  it  directly 
into  the  liquid  to  be  heated. 

A  coil  of  steam  pipe  placed  in  the  pan,  kettle  or  still  is  very 
effective  for  heating  the  contents. 

The  "steam  jacket"  consists  of  an  outer  shell  or  second  bot- 
tom riveted  and  soldered  to  the  regular  bottom  of  the  pan,  ket- 
tle or  still,  so  as  to  make  a  steam-tight  compartment  between  the 
two  bottoms  or  shells.  This  "jacket"  usually  extends  about  one- 
third  of  the  way  up  around  the  vessel,  and  leaves  a  space  of 
about  two  inches  between  the  shells  at  the  center  under  it.  The 
steam  enters  the  jacket  on  one  side  near  the  center  of  the 
bottom  through  a  horizontal  pipe  provided  with  a  globe  steam- 
valve.  The  condensed  steam  is  let  out  through  a  vertical  steam- 
pipe  fitted  to  the  outer  shell  at  its  lowest  point,  and  this  pipe 
also  has  a  valve  by  which  it  can  be  opened  or  closed.  The  side 
pipe  is  connected  by  coupling  with  the  regular  steam  supply  pipe 
and  the  outlet  pipe  at  the  bottom  is  coupled  to  another  connected 
with  the  "waste  pipe." 

A  jet  of  steam  issuing  from  the  bottom  of  a  single  shell  or  pan 
through  a  pipe  may  also  be  used  for  heating  vessels  placed  upon 
that  shell  and  fitting  it  rather  snugly,  as  a  dish  is  placed  over  a 
water-bath. 

For  heating  liquids  in  tanks,  barrels,  or  other  deep  vessels, 
steam  may  be  conducted  through  a  straight  pipe  to  the  bottom  of 
the  liquid  in  which  the  steam  condenses  giving  up  its  latent  heat 
to  the  contents.  This  method  is,  of  course,  applicable  only  in 
cases  where  there  is  no  objection  to  the  admixture  of  the  water 
from  the  condensed  steam,  and  is,  therefore,  employed  only  for 
heating  liquids  but  never  for  evaporation  or  distillation. 

For  all  ordinary  operations  where  steam-heat  is  utilized  the 

Vol.    11—13 


!Q4  FURNITURE  AND  APPARATUS. 

steam  may  be  advantageously  used  under  a  pressure  of  four 
pounds  or  even  less. 

OTHER    APPARATUS. 

356.  Earthenware  pots,  thoroughly  glazed  and  acid  proof,  are 
indispensable.    They  can  be  procured  of  all  sizes  from  5  liters  to 
300  liters,  or  even  larger.     They  are  used  for  solution,  filtration, 
precipitation,  washing,  crystallization,  etc. 

Wooden  vessels  (tubs  and  barrels)  may  be  used  for  some  spe- 
cial preparations  made  on  a  large  scale. 

Glass  and  porcelain  precipitation  jars  and  wide-mouthed  bot- 
tles are  employed  for  smaller  operations,  and  for  still  smaller 
quantities  Erlenmayer  flasks  and  beakers. 

357.  Porcelain  casseroles,  with  handles  preferably  of  wood, 
are  most  serviceable  when  of  about  i  liter's  capacity.     Porcelain 
or  "white  ware"  pitchers  may  also  be  used  to  a  considerable  extent 
for  transferring  liquids  from  one  vessel  to  another,  but  not  so 
conveniently  as  casseroles  for  hot  liquids. 

Tinware  dippers  (well  tinned)  may  be  used  for  many  purposes 
in  the  laboratory. 

358.  Bottles  for  both  solids  and  liquids,  glass-stoppered  as  well 
as    others,    are    required    in    plenty.     Glass-stoppered    so-called 
"tincture  bottles,"  for  acids  and  other  solutions,  may  be  used 
as  large  as  of  12  liters  capacity  with  great  advantage,  if  large 
quantities  of  the  liquids  are  employed ;  but  larger  bottles  are  less 
convenient  and  more  liable  to  breakage. 

359.  Evaporation  dishes  have  been  sufficiently  described  in 
Chapter  VII,  crystallizers  in  Chapter  IX,  and  mortars  and  pestles 
in  Chapter  I. 

Funnels  for  filtrations,  for  collecting  and  washing  precipitates 
and  crystals,  and  for  other  purposes  have  been  described  in  the 
chapters  discussing  those  operations,  and  flasks,  retorts,  beakers, 
wash-bottles,  and  other  requisite  glassware,  including  tubing  and 
fittings,  were  also  mentioned  to  a  sufficient  extent  in  preceding 
chapters.  Some  apparatus  will  be  more  specifically  described  in 
Part  II  as  occasion  requires. 

Sieves,  spatulas,  scoops,  spoons,  strainer  holders,  iron  stands, 
hammer  and  anvil,  cork  borer,  files,  tongs,  knives,  shears,  and 
many  other  implements  and  tools  are  needed  in  laboratories. 


FURNITURE  AND  APPARATUS.  1Q5 

The  catalogues  of  dealers  in  chemical  and  pharmaceutical  ap- 
paratus should  be  consulted  for  further  information  and  details. 
Such  catalogues  are  abundantly  illustrated. 

360.  In  the  training  laboratories  of  pharmaceutical  and  other 
technological  schools  it  is  customary  to  have  large  water-baths 
and  sand-baths,  drying  closets,  fume  chambers,  and  balance  room 
for  general  use  by  all  students,  and  to  issue  to  each  student  a  set 
of  apparatus  for  his  individual  use,  and  special:  apparatus  as  re- 
quired. 

361.  An  outfit  of  apparatus  sufficient  for  the  production  of 
experimental  quantities  of  the  great  majority  of  the  preparations 
included  in  Part  II  of  this  volume,  but  not  including  preparations 
requiring  special  apparatus,  may  be  as  follows : 

An  iron  stand  with  heavy  base  and  three  rings  of  different  sizes 
(respectively  of  75,  100  and  125  millimeters  diameter) 
on  the  rod  ("retort  stand"). 

One  copper  water-bath,  150  millimeters  diameter,  with  three 
rings,  and  with  two  opposite  handles. 

One  Russia-iron  dish,  150  millimeters  diameter  and  25  milli- 
meters deep,  for  a  sand-bath. 

A  gas  burner  (or,  in  its  place,  a  coal  oil  burner  or  a  spirit 
lamp). 

One  No.  4  or  5  mortar  and  pestle. 

One  or  two  mm  porcelain  evaporating  dishes  (Meisen  or 
Berlin  ware). 

One  or  two  graduated  glass  measures,  on  foot,  each  of  about 
200  Cc.  capacity  (metric  glass  "graduates"). 

Two  or  three  thin  glass  beakers,  of  about  250  Cc.  capacity. 

One  glass  flask  with  wide  neck  of  medium  length  and  flat  bot- 
tom, capacity  600  Cc. 

One  round  bottom  glass  flask,  600  Cc. 

One  round  glass  (or  porcelain)  dish,  about  150  millimeters 
diameter  and  35  to  50  millimeters  deep,  for  use  as  a 
crystallizer. 

One  150  mm  glass  funnel,  60°  angle,  with  long  stem  having 
beveled  end. 

One  100  mm   glass  funnel  of  same  kind. 

One  Elenmeyer  flask  of  500  Cc.  capacity. 

One  Elenmeyer  flask  of  300  Cc.  capacity. 

One  Elenmeyer  flask  of  200  Cc.  capacity. 


196  FURNITURE  AND  APPARATUS. 

One  Elenmeyer  flask  of  100  Cc.  capacity. 

One  Elenmeyer  flask  of    50  Cc.  capacity. 

One  wide-mouthed  2-liter  bottle. 

Two  wide-mouthed  i -liter  bottles. 

Two  wide-mouthed  half-liter  bottles. 

A  dozen  150  mm  test-tubes. 

One  double  ended  150  mm  horn  spatula. 

Half  a  dozen  glass  stirring  rods,  assorted  sizes,  150  to  300 
millimeters. 

Two  packages  of  coarse  (rapid  filtering)  filter  paper  ("S.  &  S.,n 
or  Swedish,  or  French)  to  fit  the  150  mm  funnel. 

One  package  of  the  same  kind  of  filter  paper  to  fit  the  100 
mm  funnel. 

Corks,  tapering,  XXX,  extra  long,  assorted  sizes. 

This  outfit  will  enable  the  student  to  make  moderate  quan- 
tities of  nearly  all  the  chemicals  mentioned  in  this  manual.  For 
the  remaining  preparations  a  few  additional  pieces  of  apparatus 
are  required,  such  as  retorts,  wash  bottles,  glass  tubing,  rubber 
tube  connections,  thistle  tubes,  perforated  rubber  stoppers,  etc. 


CHAPTER  XX. 

SOME    LABORATORY    RULES    AND    PRECAUTIONS,    AND    WHAT    TO    DO 
IN    CASE   OF    CERTAIN    ACCIDENTS 

362.  Order,  system  and  cleanliness  must  prevail  to  the  utmost 
possible  extent. 

But  as  the  materials  and  products  handled  are  generally  such 
as  would  quickly  ruin  clothing",  the  laborant  should  wear  "over- 
alls," or  at  least  apron  and  sleeves  of  rubber  cloth. 

The  laboratory  floor,  fixtures  and  furniture  must  be  kept  clean 
and  free  from  dust. 

Whenever  any  substance  is  spilled  on  a  table  or  elsewhere  the 
accident  should  receive  immediate  attention. 

Especial  care  should  be  exercised  in  handling  acids,  alkalies, 
bromine,  phosphorus,  and  other  corrosive  or  inflammable  sub- 
stances. 

Operations  attended  by  the  evolution  of  irritating  or  dangerous 
vapors  should  be  performed  out  of  doors,  or  under  the  hood  or 
fume  chamber.  When  such  operations  are  performed  outdoors 
the  operator  should  place  himself  in  such  a  position  that  the 
vapors  or  gases  evolved  are  carried  away  from  him  by  the  air 
currents. 

Reactions  liable  to  be  violent  must  be  carefully  performed, 
watched  and  controlled  to  prevent  explosions,  fire,  breakage, 
spattering  of  corrosive  or  hot  liquids,  or  the  sudden  evolution  of 
large  volumes  of  noxious  gases. 

Operations  involving  danger  should  never  be  undertaken  ex- 
cept when  necessary. 

It  must  be  remembered  that  powerful  oxidizing  agents  and 
reducing  agents  generally  react  upon  each  other  with  great 
velocity  frequently  attended  with  explosion,  fire,  or  other  dangers. 

363.  Acids  must  be  kept  in  a  safe  place  and  in  strong  contain- 
ers not  too  large  to  be  handled  with  convenience  and  with  a 
minimum  of  risk. 

Carboys  of  acids  must  not  be  moved  about,  but  should  have 
their  permanent  place  on  the  ground  or  on  a  special  stand  in  a 

197 


198  LARORATORY    RULES   AND   PRECAUTIONS. 

location  where  the  least  danger  would  result  from  their  being 
broken.  Earthenware  vessels  may  be  placed  under  the  stand  to 
catch  escaping  acids  in  case  of  breakage  of  a  carboy.  When  bot- 
tles are  rilled  from  the  .carboys,  special  acid  syphons  of  glass 
should  be  used  in  order  that  the  carboy  may  be  left  undisturbed 
in  its  position  and  to  avoid,  as  far  as  possible,  all  danger  of 
spilling. 

Whenever  a  carboy  of  acid  is  broken,  immediate  steps  must 
be  taken  to  prevent  any  greater  destruction  than  is  unavoidable. 
The  escaped  or  escaping  acid  must  be  caught  up  in  a  jar  or  dish 
if  possible,  or  neutralized  as  far  as  possible  with  sodium  carbon- 
ate, which  should  be  at  all  times  kept  near  by  for  this  purpose, 
and  plenty  of  water  should  be  turned  or  poured  upon  the  acid 
to  dilute  it.  In  order  that  this  may  be  done  quickly  and  with- 
out hesitation  or  danger,  the  acid  carboys  should  stand  in  a  place 
where  the  floor  is  covered  with  asphalt  and  inclined  toward  an 
ample  drain  connected  with  the  sewer  and  near  the  hydrant  water. 

364.  Should  the  acid  be  sulphuric  acid,  remember  that  the 
addition  of  water  will  cause  the  generation  of  great  heat  and 
steam,  and  that  the  mixture  will  be  liable  to  boil  and  spatter 
about,  especially  if  the  quantity  of  water  added  is  comparatively 
limited.     It  is,  therefore,  best  to  allow  the  acid  to  run  off  unless 
it  can  be  caught  in  a  large  earthenware  pot  or  dish.     Then  soda 
must  be  used  freely  and  a  copious  supply  of  water. 

365.  If  hydrochloric  acid  escapes  in  large  quantity  from  any 
broken  vessel,  throw  plenty  of  sodium  carbonate  upon  it,  together 
with  much  water,  and  if  the  air  gets  rilled  with  the  irritating  vapor 
scatter  some  ammonia  water  about  the  place  so  that  the  vapor 
of  ammonia  may  neutralize  that  of  the  acid. 

366.  Nitric  acid  is  more  destructive  than  any  other.     It  not 
only  attacks  with  great  vigor  any  organic  matter  with  which  it 
comes  in  contact,  but,  as  it  does  so,  it  fills  the  air  with  suffocating 
red  nitrous  vapors.     Fire  and  explosions  are  liable  to  be  caused 
by  the  action  of  nitric  acid  on  wood,  especially  if  the  wood  is 
resinous.     Sawdust  which  is  so  effective  in  absorbing  ordinary 
liquids  should  never  be  thrown  upon  acids,  especially  nitric  acid. 
When  a  large  amount  of  nitric  acid  has  escaped,  ammonia  should 
be  freely  used  to  neutralize  the  vapor  while  soda  should  also  be 
utilized,  and  an  abundance  of  water. 

In  accidents  of  this  nature  the  fire  hose  should  be  used. 


LARORATORY  RULES  AND  PRECAUTIONS.  199 

367.  When  small  quantities   of  strong  acids   are  spilled   or 
scattered  about,  they  should  be  immediately  neutralized,  diluted 
and  wiped  up.     The  eyes  and  clothing  of  laborants,  and  especially 
of  careless  and  inexperienced  beginners,  are  sometimes  destroyed 
by  acids.     The  greatest  care  should,  therefore,  be  exercised  when- 
ever any  strong  acid  is  used,  for  even  a  drop  of  it  may  easily  do 
very  serious  damage.     A  drop  or  two  of  concentrated  acid  on 
the  floor,  if  stepped  upon,  will  eat  through  the  shoe  leather;  on 
the  table  it  may  not  only  make  holes  in  the  clothing,  but  may 
find  its  way  to  hands,  face  and  eyes. 

Dilute  acids  are  also  destructive ;  they  must  be  cautiously 
handled  and  immediately  neutralized  and  thoroughly  washed  off 
when  spilled. 

368.  Strong  acids  should  never  be  directly  mixed  with  strong 
alkalies  except  in  case  of  the  escape  of  large  quantities  of  the 
acid  as   described,   and  then  only   when   plentiful   additions  >  of 
water  are  at  once  thrown  upon  the  acid,  and  it  is  dangerous  to 
be  too  near  the  spot  where  the  acid  and  alkali  are  mixed  or  to 
face  it,  for  the  temperature  of  the  reaction  is  sure  to  cause  the 
liquid  to  spatter  about. 

When  it  is  necessary  in  laboratory  operations  to  mix  a  strong 
acid  and  an  alkali  both  should  be  as  diluted  as  the  circumstances 
require,  and  they  should  be  cautiously  and  gradually  mixed  in  a 
capacious  vessel. 

369.  Water  must  never  be  added  to  strong  sulphuric  acid  for 
the  result  is   liable  to  be  disastrous   from  the  violent  reaction 
which  may  throw  considerable  portions  of  the  acid  out  of  the 
vessel   in   all   directions.     When   it   is  necessary  to   dilute   con- 
centrated sulphuric  acid  the  acid  must  be  slowly  added  to  the 
water  as  described  in  the  proper  place  in  this  book.     The  addi- 
tion of  water-solutions  of  alkalies,  ammonia,  alkali  carbonates, 
and  some  other  compounds  of  the  alkali  metals  is  even  more  dan- 
gerous than  the  addition  of  water  alone  to  strong  sulphuric  acid. 
All  water-solutions  and  also  alcoholic  liquids  act  in  a  similar 
manner  when  added  to  concentrated  sulphuric  acid. 

370.  Stock  bottles  containing  acids  must  be  strong  glass-stop- 
pered bottles,  and  not  too  large. 

Bottles  containing  volatile  acids,  such  as  nitric  acid,  hydro- 
chloric acid  and  acetic  acid,  must  not  be  entirely  filled  unless  kept 
in  a  very  cool  place,  and  when  the  bottle  is  more  than  half  filled 


2OO  .          LARORATORY  RULES  AND  PRECAUTIONS. 

with  such  an  acid  the  contents  should  be  cool  when  the  bottle  is 
opened  and  the  operator's  face  should  be  turned  away,  because 
if  the  acid  is  not  cool  there  may  be,  when  the  stopper  is  removed, 
an  out-rush  of  acid  vapor  great  enough  to  do  injury  to  the  eyes 
and  the  respiratory  organs. 

371.  All  acids  should  be  kept  in  a  cool  place. 

372.  When  a  drop  or  more  of  dilute  acid  accidentally  gets  on 
the  clothing  a  little  dilute  ammonia  should  be  applied. 

373.  Alkalies  are   not   so   dangerous   as   the   strong  mineral 
acids,  but  they  are  corrosive  enough  to  do  a  great  deal  of  damage 
if  allowed  to  come  in  contact  with  organic  matter.     They  destroy 
clothing,  and  eat  into  wood.     When  strong  lye  is  spilled  it  should 
be  at  once  diluted  with  plenty  of  water,  the  dilute  liquid  wiped 
up,  very  dilute  sulphuric  or  hydrochloric  acid  next  applied,  and 
finally  more  water. 

374.  Bottles    containing   solutions    of   potassium    hydroxide, 
sodium  hydroxide  or  ammonia  must  be  strong  glass-stoppered 
bottles;  and  bottles  containing  ammonia  solution  must  not  be 
entirely  filled,  must  be  cool  when  opened,  and  opened  cautiously, 
the  face  of  the  operator  being  averted  as  in  the  case  of  opening 
bottles  containing  volatile  acids.     Loss  of  eyesight  has  resulted 
from  opening  filled  and  not  sufficiently  cool  bottles  of  strong  am- 
monia water  owing  to  the  great  rush  of  gaseous  ammonia  from 
the  container. 

375.  When  solid  KOH  or  NaOH  is  to  be  dissolved  in  water 
it  is  best  to  add  the  alkali  to  all  of  the  water,  and  to  add  it 
gradually  if  the  solution  is  to  be  a  concentrated  one.     Great  evo- 
lution of  heat  attends  the  solution  of  the  strong  alkalies  in  water, 
probably  due  to  condensation  caused  by  molecular  combination. 

376.  The   glass   stoppers   of  bottles   containing  solutions   of 
KOH  or  NaOH  must  be  coated  with  "petrolatum."    Unless  this 
is  attended  to  it  usually  happens  that  the  stopper  becomes  so  firmly 
cemented  to  the  neck  of  the  bottle  by  the  chemical  action  of  the 
alkali  upon  the  ground  surfaces  of  the  glass  that  the  removal 
of  the  stopper  is  impossible  and  the  neck  of  the  bottle  must  be 
cut  or  broken  off  in  order  to  recover  the  contents. 

377.  Bromine  is  a  terrible  substance  to  deal  with  if  allowed  to 
escape.     It  rapidly  evaporates  and  fills  the  room  with  its  vapor, 
which  is  so  irritating  and  destructive  that  it  can  not  be  inhaled 
without  grave  danger,  and  it  attacks  the  eyes  severely.     It  also 


LARORATORY  RULES  AND  PRECAUTIONS.  2OI 

attacks  clothing,  and  the  liquid  bromine  even  eats  into  wood 
very  quickly. 

Bromine  is  necessarily  kept  in  comparatively  small,  strong, 
glass-stoppered  bottles,  but  the  stoppers  usually  become  fast  in 
the  necks  of  the  bottles  so  that  their  removal  is  in  some  cases 
impracticable.  It  is  then  necessary  to  cut  or  break  the  neck  off, 
or  to  break  the  bottle  itself,  to  empty  it  when  the  bromine  is  to  be 
used.  This  is,  of  course,  a  hazardous  operation  unless  the 
operator  is  expert  or  careful  and  takes  such  precautions  as  will 
prevent  the  liability  to  serious  results.  When  the  bromine  bottle 
is  to  be  opened  it  should  be  held  over  and  near  the  bottom  of  a 
strong  porcelain  dish,  and  this  in  turn  should  be  placed  in  a 
second  strong  porcelain  dish.  At  the  same  time  an  empty  glass 
stoppered  bottle  with  a  small  funnel  already  placed  in  its  neck 
should  be  at  hand  into  which  the  bromine  can  be  at  once  trans- 
ferred from  the  original  bottle  or  from  the  porcelain  dish  should 
the  original  bottle  be  broken  to  such  an  extent  that  the  bromine 
runs  out  into  the  dish.  The  whole  operation  should  be  per- 
formed either  outdoors,  or  under  the  fume  hood,  or  on  the  ledge 
outside  the  window. 

Whenever  the  bromine  is  to  be  used  with  water  for  some 
laboratory  operation,  as,  for  instance,  in  making  bromide  if  iron, 
it  is  best  to  open  the  bottle  of  bromine  over  a  porcelain  dish  con- 
taining water,  or  to  break  the  bottle  in  the  body  of  the  water  in 
the  dish.  The  weight  of  the  water  must  then  be  known  before 
the  bromine  is  added,  or  the  gross  weight  of  bromine  and  bottle, 
or  both,  and  the  tare  of  the  bromine  bottle  found  in  some  way. 
The  bromine  and  water  can  be  transferred  from  the  dish  to  a 
tared  flask  or  some  other  vessel  and  there  weighed,  the  fragments 
of  the  bottle  remaining  in  the  dish. 

The  neck  of  a  bottle  is  best  broken  off  by  first  filing  a  deep 
groove  around  it  and  then  striking  it  gently. 

When  large  quantities  of  bromine  are  used  the  bottles  should  be 
put  in  a  safe,  cool  place,  preferably  out  in  the  yard  and  buried  in 
a  mound  of  sand  or  clay  by  which  the  bromine  might  be  partially 
absorbed  should  any  bottle  be  broken. 

In  case  of  the  escape  of  bromine  in  the  room  a  liberal  quan- 
tity of  sodium  carbonate  or  potassium  carbonate  should  be  as 
quickly  as  possible  thrown  upon  it  after  which  plenty  of  water 
should  be  added.  Ammonia  water  should  be  scattered  on  the 


2O2  LARORATORY  RULES  AND  PRECAUTIONS. 

floor  near  the  bromine  in  order  that  the  vapors  of  the  H3N  and 
the  Br2  may  neutralize  each  other. 

If  liquid  bromine  is  allowed  to  act  upon  any  part  of  the  body 
it  may  quickly  produce  serious  wounds  which  are  not  only  very 
painful  but  quite  difficult  to  heal. 

The  vapor  attacks  the  eyes  and  face  and  the  respiratory  organs. 
Should  the  effects  be  so  severe  as  to  require  alleviation  a  little 
ammonia  vapor  may  be  very  cautiously  inhaled  from  diluted  am- 
monia water,  and  the  face  and  eyes  freely  bathed  with  cold  water. 

378.  Phosphorus,  and  also  the  metals  potassium  and  sodium, 
are  fire-dangerous. 

Phosphorus  must  be  kept  in  water  contained  in  glass-stop- 
pered bottles  in  a  safe  place.  When  required  for  use  it  must  be 
handled  and  divided  in  water  or  in  a  moist  condition,  and  it  can 
not  be  with  safety  wiped  dry  for  weighing.  Should  it  ignite 
it  must  be  at  once  thrown  into  water.  If  ignited  while  held  in 
the  hand  or  between  the  fingers  it  may  cause  severe  wounds. 

Potassium  and  sodium  must  be  kept  in  a  liquid  hydrocarbon  in 
tightly  stoppered  bottles.  They  ignite  when  exposed  to  the  air 
or  come  in  contact  with  water. 

379.  Ether,  petroleum  spirit  (benzin)  and  other  inflammable 
liquids  must  be  kept  in  strong,  tightly  closed  containers   (not 
filled)   in  a  cool  place,  away  from  any  light  or  fire,  and  when 
required  for  use  they  should  not  be  brought  near  any  flame.     It 
must  always  be  remembered  that  the  vapors  of  inflammable  vola- 
tile liquids  may  be  conveyed  through  and  with  the  air  and  be- 
come ignited  by  a  flame  a  considerable  distance  from  the  vessel 
containing  the  liquids.     Extraordinary  precautions  must  be  taken 
to  prevent  fire  when  any  distillation  or  other  operation  is  per- 
formed in  which  a  volatile  inflammable  liquid  is  heated.    All  such 
operations  should  be  performed  on  the  fire  table  near  the  sink 
and  in  such  manner  that  the  inflammable  vapor  can  not  come  in 
contact  with  the  flame  indirectly  or  directly  supplying  the  heat. 

Inflammable  vapors  form  explosive  mixtures  with  air. 

380.  Fire  in  a  laboratory  may  be  caused  not  only  by  strong 
acids,  phosphorus,  ether  and  other  inflammables  and  explosives, 
but  more  easily  than  elsewhere  from  the  careless  handling  of 
matches  and  heating  apparatus,  because  heat  is   so   constantly 
utilized.     Strict   discipline  in  this   direction   is  accordingly   im- 
perative. 


LARORATORY   RULES   AND   PRECAUTIONS.  2O3 

Matches  must  be  kept  in  a  safe  place.  Gas  should  never  be 
left  burning  except  when  necessary.  Water-baths  should  never 
be  permitted  to  become  empty  while  in  use. 

Whenever  the  laboratory  is  about  to  be  closed  for  the  night, 
or  temporarily  deserted  at  any  time,  a  careful  inspection  must  be 
made  to  see  that  no  flame  of  any  kind  is  left  burning  and  no 
operation  continued  which  is  liable  to  prove  dangerous  or  to  cause 
any  injury  or  loss  by  fire,  explosion,  or  any  damage  to  materials, 
or  to  products  in  process  of  preparation. 

In  the  training  laboratories  of  technical  schools  the  employment 
of  common  large  sand-baths  and  water-baths  for  the  use  of  the 
classes  diminishes  the  liability  to  danger  and  damage  by  rendering 
unnecessary  the  constant  use  of  gas  burners  as  well  as  by  sub- 
stituting the  far  safer  baths  for  many  operations  in  which  in- 
flammable substances  are  employed. 

Operations  and  experiments  involving  danger  can  be  entirely 
avoided  in  college  laboratories,  and  the  risks  of  accidents  be  thus 
reduced  to  such  as  may  happen  anywhere  as  the  result  of  gross 
carelessness  or  stupidity. 

381.  In  all  laboratory  work  the  operators  should  keep  a 
journal  or  record  of  every  operation  and  of  each  important  step 
in  it.  To  save  time  it  is  generally  advantageous  or  even  neces- 
sary to  keep  two,  three  or  even  more  preparations  under  way 
concurrently. 

All  vessels  containing  either  materials,  unfinished  products,  or 
finished  products  must  be  labeled  so  explicitly  that  no  mistake 
can  be  made.  To  leave  any  substance,  or  mixture,  or  solution, 
unlabeled,  trusting  to  memory  to  know  what  it  is,  must  be  re- 
garded as  inadmissible  in  a  laboratory.  Nothing  should  be  left 
unlabeled  for  even  an  hour.  The  label  on  the  vessel  should  not 
only  indicate  plainly  what  it  contains  but  what  the  contents  are  to 
be  used  for,  the  date,  and  also  the  name  of  the  laborant  having 
the  matter  in  hand. 

Notes  should  be  made  in  the  laboratory  journal  of  all  prepara- 
tions made,  date  when  commenced,  materials  used  and  quantities 
of  them,  method  adopted  (if  there  is  a  choice),  any  interesting, 
instructive  or  important  observations  made  in  regard  to  the 
results,  the  date  on  which  the  preparation  is  finished,  the  quan- 
tity of  product  obtained  and  its  character  or  quality,  and  what 
was  done  with  the  bye-product,  if  anything. 


2O4  LARORATORY  RULES  AND  PRECAUTIONS. 

382.  Unnecessary  delay    in  finishing  the  operations   under- 
taken in  the  laboratory  is  very  liable  to  cause  loss  or  waste  of 
materials  as  well  as  of  the  time  and  labor  already  bestown.    This 
applies  to  analytical  processes  as  well  as  to  the  production  of 
chemical  preparations.     No  preparation  should  be  started  at  an 
hour  when  it  would  be  impracticable  to  give  it  the  attention 
necessary  to  carry  the  process  up  to  a  point  at  which  further  at- 
tention may  be  deferred  without  disadvantage  or  risk. 

Unfinished  products,  especially  if  moist,  are  generally  more 
liable  to  decomposition  or  damage  from  exposure  than  finished 
preparations. 

383.  How  to  clean  apparatus.     All  laboratory  apparatus  and 
implements,  as  well  as  the  furniture,  must  be  kept  clean.     Opera- 
tors who  do  not  clean  their  apparatus  and  utensils  thoroughly  and 
keep  them  in  perfect  order  and  ready  for  use,  and  who  leave  the 
table  in  disorder,   soiled    or    wet,   are  wholly  unfit    laborants. 
Every  piece  of  apparatus  should,  after  using  it,  be  as  thoroughly 
cleaned  as  any  dish,  plate  or  tumbler  set  before  properly  fastidious 
persons  at  the  dinner  table. 

But  chemical  apparatus,  and  especially  mortars  and  pestles, 
require  at  times  chemical  agencies  to  clean  them,  particularly  if 
they  have  been  permitted  to  remain  long  in  contact  with  sub- 
stances which  act  upon  them  chemically  or  which  are  absorbed. 

"Dirt  is  only  misplaced  matter,"  and  even  pharmacists  and 
chemists  are  apt  to  recognize  or  notice  only  colored  dirt.  But 
white  or  colorless  dirt  is  quite  as  objectionable  and  sometimes 
more  so  than  the  more  obtrusive  kinds.  Hence  all  chemical  and 
pharmaceutical  apparatus  must  be  scrupulously  cleaned  and 
rinsed. 

Insoluble  substances  rubbed  into  the  pores  of  mortars  and 
pestles  or  adhering  to  glass  and  glazed  surfaces  should  be  con- 
verted into  soluble  substances  to  facilitate  their  removal.  Thus 
iron  stains  may  be  removed  with  the  aid  of  nitric  acid  or  hydro- 
chloric acid,  or,  if  necessary,  both  together;  insoluble  mercury 
compounds  are  removed  with  nitric  acid ;  antimony  compounds 
with  strong  hydrochloric  acid ;  iodine  stains  with  potash  solution ; 
organic  extractive  with  strong  potash  solution;  arsenic  and  its 
compounds  with  strong  nitric  acid ;  silver  compounds  with  strong 
ammonia  or  with  nitric  acid,  or  the  two  used  alternately;  lead 
compounds  with  nitric  acid,  etc. 


LARORATORY   RULES   AND   PRECAUTIONS.  2O5 

The  piece  of  apparatus  cleaned  may  be  known  to  be  free  from 
the  substances  sought  to  be  removed  when  their  presence  can  no 
longer  be  detected  by  means  of  sensitive  reagents.  To  simply 
turn  colored  dirt  into  colorless  dirt  by  means  of  chemicals  is  not 
to  remove  it ;  invisible  dirt,  if  not  removed,  can  usually  be  easily 
enough  rendered  visible  by  reagents. 


PART  II. 


LABORATORY  MANUAL  OF  INORGANIC 
CHEMICAL  PREPARATIONS. 


LABORATORY  MANUAL. 


INTRODUCTORY. 


The  chemical  products  for  which  methods  of  preparation  are 
here  given  include  all  of  the  inorganic  compounds  commonly 
employed  in  every  day  life,  in  the  chemical  arts  and  industries, 
and  in  medicine  and  pharmacy,  together  with  many  interesting 
and  instructive  preparations  which  are  not  much  used.  The  inor- 
ganic preparations  of  the  pharmacopoeias  are  all  included. 

Processes  attended  with  great  danger  or  difficulty,  and  such  as 
require  expensive  and  unusual  apparatus,  have  been  omitted. 

The  nomenclature  is,  as  will  be  seen,  a  technical  English 
nomenclature,  and  the  corresponding  latinic  titles  have  been  given 
a  subordinate  position,  together  with  the  most  common  non-tech- 
nical names  and  officinal  designations. 

The  proportions  and  quantities  specified  in  the  formulas  are  as 
a  rule  reduced  to  the  simplest  terms  and  the  method  of  expres- 
sing the  proportions  in  "parts  by  weight"  has  been  very  largely 
employed ;  but  when  circumstances  seemed  to  require  it  the  quan- 
tities of  solids  have  been  expressed  in  Grams  (Gm)  and  those  of 
liquids  in  milliliters  (ml). 

In  large  practice  laboratories  it  is  rarely  practicable  to  weigh 
all  liquids,  while  it  is  very  easy  to  measure  them  in  graduated 
glass  measures ;  and  in  most  cases  the  quantities  required  can  be 
measured  with  sufficient  accuracy  to  insure  entirely  satisfactory 
results.  Students  can  readily  find  the  number  of  milliliters  cor- 
responding to  any  given  number  of  Gm  by  dividing  the  number 
of  Gm  by  the  specific  weight  or  multiplying  that  number  by  the 
specific  volume  (which  is  the  reciprocal  of  the  specific  weight). 
Quantities  of  liquids  below  5  ml  or  above  500  ml  should  be 
weighed  instead  of  being  measured. 

When  these  formulas  are  employed  in  college  laboratories  for 
practice  in  preparation  work  it  is  suggested  that  the  lessons  be 

209 

Vol.    11—14 


2IO  INTRODUCTORY. 

to  some  extent  so  selected  that  the  product  obtained  from  each 
may  serve  as  one  of  the  materials  for  the  next  lesson.  The  stu- 
dent may,  for  instance,  first  be  given  the  iron  and  sulphuric  acid 
to  make  ferrous  sulphate ;  he  may  then  make  not  only  ferrous 
sulphate  in  large  crystals,  but  also  turbidated  and  precipitated  fer- 
rous sulphate,  dried  ferrous  sulphate,  ferric  sulphate,  ferric  sub- 
sulphate,  ferric  hydroxide,  ferric  pyrophosphate,  ferric  citrate, 
etc.  He  may  be  furnished  the  materials  for  the  preparation  of 
sodium  phosphate  and  then  make  several  phosphates  and  pyro- 
phosphates  from  the  same  materials.  It  is  also  useful  to  require 
students  to  recover  the  bye-products  wherever  practicable,  and 
to  account  for  the  materials  furnished  them  by  producing  as  large 
a  yield  of  each  product  as  may  be  practically  obtainable. 

The  directions  and  notes  are  sufficiently  explicit  to  enable  in- 
dividual students  as  well  as  other  laborants  to  do  the  work  suc- 
cessfully and  saticfactory  results  are  certainly  unattainable  with- 
out such  explanations  as  can  not  be  repeated  to  each  individual 
student. 

The  working-formulas  included  in  this  work  are  applicable  not 
only  in  the  practice  laboratories  of  technical  schools,  but  also 
in  the  laboratories  of  manufacturing  pharmacists  and  chemists. 


WEIGHTS   AND   MEASURES. 


All  weights  and  measures  in  use  in  the  United  States  of 
America  are  derived  from  the  metric  prototypes  in  the  custody 
of  the  Office  of  Standard  Weights  and  Measures  at  Washington. 
The  prototypes  referred  to  are  the  U.  S.  National  Prototype 
Standard  Meter  and  the  U.  S.  National  Prototype  Standard 
Kilogram,  both  made  of  iridium-platinum  and  furnished  to  the 
American  Government  by  the  International  Bureau  of  Weights 
and  Measures  in  1890. 

The  old  customary  weights  and  measures,  as  well  as  those 
of  the  metric  system,  are  based  upon  and  adjusted  to  the  material 
metric  standards  mentioned. 

THE    METRIC    SYSTEM. 

The  meter  is  the  length  of  iridium-platinum  prototype  meter  at 
Washington. 

i  meter  is  equal  to  10  decimeters. 

i  meter  is  equal  to  100  centimeters. 

I  meter  is  equal  to  1000  millimeters  (mm). 

The  kilogram  is  the  mass  of  'the  iridium-platinum  prototype 
kilogram  at  Washington. 

i  kilogram  is  equal  to  1000  grams  (Gm). 

i  gram  is  equal  to  1000  milligrams  (mGm). 

The  liter  is  the  volume  of  one  kilogram  of  pure  water  at  4°  C. 
in  vacuo. 

i  liter  is  equal  to  1000  milliliters  (ml). 

[Theoretically  the  volume  of  i  kilogram  of  pure  water  at  4°  C. 
in  vacuo  is  i  cubic-decimeter;  but  the  liter  in  actual  use,  being 
always  obtained  by  weight,  can  not  consistently  be  called  a  cubic- 
decimeter,  especially  as  it  seems  probable  that  the  actual  liter 
measures  less  than  a  cubic-decimeter.] 

i  cubic-decimeter  is  equal  to  1000  cubic-centimeters  (Cc.). 

I  American  yard  is  |^  meter. 

i  American  commercial  pound  is  j^^^,  kilogram, 
i   American  liquid  gallon  is  the  volume  of  3785.434  Gm    of 
pure  water  at  4°  C.  in  vacuo. 

211 


WATER. 


AQUA. 


The  Pharmacopoeia  of  the  United  States  defines  "aqua"  as 
"natural  water  in  its  purest  attainable  state."  •  It  must  be  color- 
less, clear,  inodorous,  and  tasteless.  Should  not  contain  more 
than  100  milligrams  of  fixed  impurities  in  one  liter,  and  not  more 
than  traces  of  organic  matter. 

Spring  water  usually  contains  inorganic  salts,  consisting  chiefly 
of  the  chlorides,  sulphates  and  carbonates  of  calcium,  mag- 
nesium, etc.  Such  water  is  called  hard  water,  because  when  used 
with  soap  it  produces  insoluble  compounds,  which  cause  a  sense 
of  harshness.  Hard  water  can  be  rendered  less  so  by  boiling  it, 
because  the  calcium  and  magnesium  carbonates,  which  are  held 
in  solution  by  the  carbonic  acid  present,  deposit  as  soon  as  that 
acid  is  expelled  by  the  heat.  Spring  water  is  generally  unfit  for 
pharmaceutical  uses  on^  account  of  the  mineral  impurities  it  con- 
tains. 

Well  water  often  contains  organic  matter  derived  from  sew- 
age, etc.,  especially  in  thickly  inhabited  places,  and  must  not  be 
used  unless  careful  examination  shows  it  to  be  sufficiently  pure. 
Water  contaminated  with  organic  substances  contains  ammonia. 
The  presence  of  organic  matter  in  sufficient  quantity  to  impart 
odor  to  the  water  should  at  once  condemn  it.  Where  pure  water 
is  not  obtainable  for  ordinary  purposes,  small  quantities  of  organic 
impurities  may  be  partially  removed  by  adding  a  little  alum  ;  the 
ammonia  and  carbonates  present  cause  the  precipitation  of 
aluminum  hydrate,  which,  as  it  settles,  carries  other  impurities 
with  it. 

Rain  water  is  pure  if  collected  in  clean  vessels  as  it  descends 
from  the  clouds  after  the  rain  has  continued  long  enough  to 
purify  the  atmosphere  from  dust,  etc.  Falling  off  roofs  and  col- 
lected from  the  conduits  in  the  usual  way  it  is  rarely  pure. 

Ice,  when  melted,  affords  a  comparatively  pure  water. 

212 


WATER.  213 

River  and  lake  water,  containing  usually  but  small  amounts 
of  calcium  and  magnesium  salts,  is  called  soft  water,  and  is  fre- 
quently pure  enough  for  most  purposes ;  it  may,  however,  contain 
both  organic  and  inorganic  impurities. 

Uses.  Water  is  indispensable  in  medicine,  pharmacy,  chem- 
istry, as  well  as  in  the  household  economy.  It  is  the  best  solvent 
and  diluent  we  have,  being  abundant,  and  capable  of  dissolving 
a  great  variety  of  substances.  It  is,  moreover,  chemically  indif- 
ferent or  neutral  to  most  substances,  and  hence  affords  a  means 
of  reducing  water-soluble  substances  to  a  liquid  condition  with- 
out otherwise  altering  their  properties,  and  can  be  freely  used  to 
facilitate  many  chemical  reactions. 

Tests.  Mix  100  ml  of  the  water  with  10  ml  of  diluted  sul- 
phuric acid;  heat  to  boiling;  then  add  enough  solution  of  potas- 
sium permanganate  (i  part  to  1000  parts  of  distilled  water)  to 
give  to  the  mixture  a  distinct  rose-red  color ;  then  boil  for  five 
minutes.  The  color  will  not  be  entirely  destroyed  by  this  treat- 
ment unless  more  than  traces  of  organic  matter  be  present. 

DISTILLED   WATER — AQUA   DESTILLATA. 

Water,  a  convenient  quantity. 

Put  the  water  into  a  suitable  still  of  copper  or  tinned  iron,  the 
still  to  be  about  two-thirds  filled.  Connect  it  with  a  suitable 
condenser,  and  distil.  The  first  portion  that  passes  over  is  to 
be  rejected,  being  contaminated  with  impurities  taken  up  in  its 
passage  through  the  apparatus,  and  containing  also  any  carbonic 
acid  or  other  volatile  substances  which  may  have  been  present 
in  the  water. 

When  only  about  one-fifth  or  one-sixth  of  the  water  remains 
in  the  still,  the  process  is  to  be  arrested  in  order  to  prevent  pos- 
sible contamination  with  products  of  decomposition  of  organic 
substances  by  overheating. 

In  large  laboratories  it  is  necessary  that  a  special  distilling 
apparatus  be  exclusively  devoted  to  the  preparation  of  distilled 
water. 

The  most  effective  and  satisfactory  plan  is  to  use  a  small  boiler 
of  the  simplest  construction  permanently  placed  in  brick  work 
over  a  fireplace  with  good  draft.  Before  the  water  to  be  dis- 
tilled is  put  in  the  boiler  it  may  be  advantageously  treated,  first 


214  WATER. 

with  a  little  potassium  permanganate  and  then  with  alum.  The 
first  portion  of  the  distillate  should  be  rejected  as  long  as  it  does 
not  hold  the  necessary  tests. 

Distilled  water  may  be  kept  in  large  bottles  the  necks  of  which 
are  closed  by  loose  plugs  of  pure  cotton  (''absorbent  cotton")  in- 
stead of  glass  stoppers. 

Tests.  Should  yield  no  residue  on  evaporation.  In  applying 
the  permanganate  test  described  above  to  distilled  water,  the 
rose-red  tint  should  not  only  remain  after  five  minutes'  boiling, 
but  should  not  be  entirely  destroyed,  even  after  ten  hours'  stand- 
ing in  a  covered  vessel  subsequent  to  the  boiling. 

It  should  not  be  affected  by  test-solutions  of  barium  chloride 
(sulphates),  silver  nitrate  (chlorides),  ammonium  oxalate  (cal- 
cium), or  mercuric  chloride  with  or  without  the  subsequent  addi- 
tion of  potassium  carbonate  (ammonia  and  ammonium  com- 
pounds). 


ACIDS. 

Caution  in  the  handling  and  use  of  acids  has  been  urged  in  the 
chapter  devoted  to  laboratory  rules  and  precautions.  The  most 
suitable  containers  for  constant  use  in  the  laboratory  are  the 
common  glass  stoppered  "acid  bottles"  of  about  two  liters  ca- 
pacity. 

The  removal  of  the  glass  stopper  which  has  become  fast  in  the 
neck  of  an  acid  bottle  is  attended  with  risk.  Gently  tapping  the 
stopper  with  a  wooden  block  or  stick,  warming  the  neck  of  the 
bottle  with  a  cloth  dipped  in  hot  water  or  by  cautiously  rotating 
it  while  held  over  the  flame  of  a  gas  burner  or  spirit  lamp,  and 
inverting  the  bottle  in  a  vessel  containing  enough  warm  water  to 
cover  the  whole  bottle-neck,  are  among  the  best  means  of  loosen- 
ing the  stopper  sufficiently  to  render  the  application  of  the 
stopper  wrench  successful.  A  block  of  wood  with  a  deep  groove 
in  the  center  is  an  effective  stopper  wrench.  If  the  bottle  is 
nearly  rilled  and  the  acid  volatile  (as  nitric,  hydrochloric  or 
acetic  acid)  and  concentrated,  the  face  should  be  turned  away 
when  the  stopper  is  removed. 

The  acids  of  different  manufacturers  and  different  pharma- 
copoeias are  not  of  uniform  strength.  It  is,  therefore,  important 
that  the  laborant  should  know  the  particular  strength  intended 
by  the  directions  or  formula  followed,  and  the  strength  of  the 
acid  he  actually  employs  in  order  that  the  quantities  or  proportions 
may  be  adjusted  as  the  circumstances  may  require.  The  em- 
ployment of  acids  which  are  stronger  or  weaker  than  those  pre- 
scribed by  the  manual  is  often  practicable  if  the  quantities  be 
modified  accordingly;  but  in  many  cases  the  particular  strength 
prescribed  can  not  be  altered  without  disadvantage  or  failure. 

As  the  acids  are  so  many  and  so  extensively  used,  and  as  many 
metallic  salts  of  the  organic  acids  must  necessarily  be  included 
in  any  such  manual  as  this,  all  of  the  common  acids,  organic  as 
well  as  inorganic,  are  placed  together  in  alphabetical  order  under 
the  general  head  of  acids  before  the  other  compounds  are  de- 
scribed. 

215 


2l6  ACIDS. 

ACETIC   ACID. 

ACIDUM    ACETICUM. 

HC2H3O2=6o. 

Formerly  prepared  by  acetic  fermentation  of  dilute  alcohol, 
or  of  weak  saccharine  liquids.  It  is  now  made  by  dry  distillation 
of  wood.  Oakwood  billets  are  heated  in  closed  sheet-iron  cylin- 
ders, one  of  the  numerous  products  being  impure  acetic  acid,  or 
wood  vinegar,  which  is  afterwards  purified. 

The  impure  acetic  acid  obtained  by  the  destructive  distillation 
of  wood  is  called  pyroligneous  acid,  and  has  a  disagreeable  smoky 
odor  from  the  empyreumatic  products  contained  in  it.  Even 
some  of  the  better  grades  of  acetic  acid  contain  empyreumatic 
matters,  and  only  chemically  pure  acid  is  entirely  free  from  them. 
To  get  rid  of  these  impurities  the  acid  is  treated  with  lime  and 
soda,  the  acetates  of  calcium  and  sodium  are  freed  from  the  tarry 
matters,  and  then  decomposed  by  sulphuric  or  hydrochloric  acid. 
A  nearly  pure  acetate  of  sodium  can  thus  be  made  from  the  impure 
acid,  and  by  distilling  a  mixture  of  this  sodium  acetate  with  sul- 
phuric acid  a  purer  grade  of  acetic  acid  is  obtained,  which  can 
be  further  purified  by  again  neutralizing  with  sodium  carbonate, 
decomposing  the  acetate  with  sulphuric  acid,  and  distilling  as 
before.  A  pure  sodium  acetate  is  finally  obtained,  from  which 
pure  acetic  acid  may  be  made  as  follows : 

Sodium  acetate 18  parts 

Sulphuric  acid    13  parts 

Reduce  the  acetate  to  a  coarse  powder ;  introduce  it  into  a  dis- 
tilling flask;  warm  the  flask;  connect  it  with  a  condenser  and 
receiver ;  add  the  sulphuric  acid  through  a  funnel  tube,  a  little  at 
a  time,  and  continue  the  distillation  until  12  parts  of  distillate 
have  been  collected. 

Test  the  product  with  volumetric  test-solution  of  potassium 
hydroxide  to  determine  its  strength  and  then  dilute  as  required. 

Properties.  A  solution  composed  of  36  per  cent  of  hydrogen 
acetate  and  64  per  cent  of  water. 

A  clear,  colorless  liquid,  of  a  distinctly  vinegar-like    odor,    a 


ACIDS.  217 

purely  acid  taste,  and  a  strongly  acid  reaction.  Sp.  gr.  1.048  at 
I5°C,  compared  with  water  at+4°  C.  as  i.ooo.  Its  specific  vol- 
ume is  accordingly  0.954.  Miscible  in  all  proportions  with  water 
and  alcohol,  and  wholly  volatilized  by  heat. 

The  presence  of  empyreuma  is  at  once  detected  by  a  smoky 
odor  when  the  acid  is  neutralized  with  KOH,  NaOH,  or  KHCO3. 

An  acetic  acid  of  from  77  to  80  per  cent  strength  has  the  sp.  w. 
of  about  1.0748;  weaker  and  stronger  solutions  of  acetic  acid 
have  a  lower  specific  weight.  Hence  the  strength  of  acetic  acid 
can  not  be  determined  otherwise  than  by  actual  assay. 

Valuation.  To  neutralize  6  Gm  of  acetic  acid  containing  36 
per  cent  of  absolute  HC2H3O2  requires  36  ml  of  normal  volu- 
metric test-solution  of  potassium  hydroxide  .  (Each  ml  required 
of  the  test-solution  indicates  i  per  cent  of  absolute  acetic  acid.) 
Phenolphtalein  is  the  indicator  usually  employed. 

Diluted  Acetic  Acid. 

Acetic  acid    100  Gm 

Distilled  water    500  Gm 

Mix  them. 

Description. — Diluted  acetic  acid  contains  6  per  cent,  by  weight, 
of  absolute  acetic  acid. 

Specific  gravity:  about  1.008  at  15°  C. 

It  corresponds,  in  properties,  to  Acetic  Acid  (see  Acidum 
Aceticuiii),  and  should  respond  to  the  same  tests  of  purity. 

To  neutralize  24  Gm  of  diluted  acetic  acid  should  require  24  ml 
of  potassium  hydroxide  test-solution  (each  ml  corresponding  to 
0.25  per  cent  of  the  absolute  acid),  phenolphtalein  being  used  as 
indicator. 

Glacial  Acetic  Acid. 
Nearly  or  quite  absolute  acetic  acid. 

Description. — At  or  below  15°  C.  (59  F.)  a  crystalline  solid;  at 
higher  temperatures  a  colorless  liquid.  When  liquefied  and  as 
near  as  possible  to  15°  C.  it  has  the  sp.  gr.  1.056 — 1,058.  Its 
properties  are  similar  to  those  of  acetic  acid,  and  it  is  similarly 
affected  by  reagents. 


2l8  ACIDS. 

To  neutralize  3  Gm  of  glacial  acetic  acid  should  require  not 
less  than  49.5  ml  of  normal  solution  of  potassium  hydroxide  (cor- 
responding to  at  least  99  per  cent  of  absolute  acetic  acid). 

At  low  temperatures  it  crystallizes  into  an  ice-like  mass,  and 
when  it  only  partially  congeals  it  has  the  appearance  of  a  supersat- 
urated solution. 

When  glacial  acetic  acid  is  diluted  with  water  its  specific  gravity 
increases  with  a  simultaneous  fall  in  temperature  until  the  mix- 
ture contains  about  77  to  80  per  cent  of  hydrogen  acetate.  Upon 
the  further  addition  of  water,  however,  the  specific  gravity  de- 
creases and  the  temperature  of  the  mixture  rises.  An  acetic  acid  of 
47  per  cent  strength  has  the  same  specific  gravity  as  the  official 
glacial  acetic  acid,  which  is  more  than  twice  as  strong. 

The  corrosive  nature  of  glacial  acetic  acid  renders  it  neces- 
sary to  be  very  cautious  in  handling  it,  especially  in  removing 
the  stopper  from  a  full  bottle  which  has  been  standing  in  a  warm 
place,  as  vapors  of  the  acid  are  liable  to  issue  from  the  bottle  with 
a  rush  at  the  moment  the  stopper  is  removed. 

Glacial  acetic  acid  is  a  remarkably  effective  solvent  for  resins, 
volatile  oils,  glucosides,  alkaloids,  and  many  other  organic  sub- 
stances. It  also  dissolves  normal  bismuth  nitrate. 


BENZOIC   ACID. 

ACIDUM    BENZOICUM. 
HC7H5O2=I22. 

Benzoic  acid  is  contained  in  benzoin  to  the  extent  of  from  10 
to  19  per  cent  and  may  be  obtained  by  sublimation.  The  benzoin 
is  coarsely  powdered  and  spread  in  a  thin  layer  on  a  flat  tinned 
iron  pan.  This  pan,  for  500  Gm  of  benzoin,  ought  to  be  about 
300  mm  in  diameter  and  about  35  mm  deep.  A  sheet  of  porous 
paper  is  fastened  over  the  pan,  after  which  a  cone  or  dome  of 
thick  paper  is  tied  securely  around  the  edges  of  the  pan.  The 
apparatus  is  then  placed  on  an  iron  plate,  covered  with  a  thin  layer 
of  sand.  Heat  is  now  applied,  gradually,  until  the  odor  of  benzoic 
acid  becomes  quite  noticeable  through  the  paper,  but  the  tempera- 
ture must  not  be  raised  too  high,  for  the  product  will  then  become 
fused  and  discolored. 


ACIDS.  219 

Benzoic  acid  can  also  be  made  by  the  wet  way :  boiling  benzoin 
with  calcium  or  sodium  hydroxide,  and  decomposing  the  benzoate 
of  calcium  or  sodium  with  hydrochloric  acid.  Sodium  carbonate 
may  also  be  used : 

Benzoin    4  parts 

Sodium  carbonate I  part 

Hydrochloric  acid,  sufficient. 

Digest  the  benzoin  with  the  sodium  carbonate,  previously  dis- 
solved in  10  parts  of  water,  for  three  hours  at  about  60°  C.  Then 
boil  the  mixture  a  few  minutes,  filter,  and  neutralize  with  hydro- 
chloric acid.  Collect  the  precipitated  benzoic  acid,  and  purify  it 
by  dissolving  it  in  20  times  its  weight  of  boiling  water,  digesting 
the  solution  with  a  little  animal  charcoal,  filtering,  concentrating 
the  solution  by  evaporation,  and  crystallizing. 

Benzoic  acid  is  now  manufactured  chiefly  from  toluol ;  but  also 
from  hippuric  acid  and  from  naphthalin.  This  artificial  benzoic 
acid  is  generally  pure,  chemically,  but  differs  from  pure  natural 
benzoic  acid  by  being  more  compact  and  inodorous.  Natural 
benzoic  acid  obtained  from  benzoin  by  sublimation,  is  very  soft 
and  bulky,  and  is  fragrant.  Benzoic  acid  prepared  from  benzoin 
by  the  wet  process  is,  however,  scarcely  fragrant.  The  agreeable 
odor  of  sublimed  benzoic  acid  seems  to  be  due  to  ethyl  benzoate, 
or  to  some  volatile  oil,  or  both,  existing  in  the  resin  and  accom- 
panying the  acid  when  sublimed.  The  fragrant  benzoic  acid  pre- 
pared from  benzoin  by  sublimation  is  the  only  kind  prescribed  by 
several  pharmacopoeias. 

In  the  trade  the  natural  benzoic  acid  is  styled  as  "English,"  and 
the  artificial  as  "German  Benzoic  Acid." 

Benzoic  acid  has  marked  antiseptic  properties,  and  a  solution 
of  one  part  of  benzoic  acid  and  one  part  of  borax  in  100  parts  of 
water  is  often  employed.  The  borax  aids  the  solution  of  the 
benzoic  acid. 

Benzoic  acid  must  be  kept  in  tightly  closed  bottles,  in  a  cool 
place,  and  well  protected  against  light. 

Description. — Natural  benzoic  acid  (that  prepared  from  Siam 
benzoin  by  sublimation)  is  white  or  yellowish  white,  in  scales  or 
needles  of  silky  lustre,  and  has  an  agreeable  benzoin-like  odor 
and  a  somewhat  pungent  taste.  Melts  at  120°. 


220  ACIDS. 

Artificial  benzole  acid  is  white,  consists  of  lustrous  needles,  is 
odorless,  and  has  a  warm,  acid  taste.  Melts  at  i2i.°4. 

Benzoic  acid  is  soluble  at  15°  in  about  400  parts  of  water,  and  in 
2  parts  of  alcohol;  in  17  parts  of  boiling  water,  and  in  I  part  of 
boiling  alcohol ;  also  in  2.5  to  3  parts  of  ether  and  in  10  parts  of 
glycerin.  It  is  also  soluble  in  fixed  and  in  volatile  oils. 


BORIC   ACID. 

ACIDUM     BORICUM. 

H3B03=62. 

Borax,  in  powder 100  parts 

Nitric  acid  (63% ) .     58  parts 

Distilled  water. 

Dissolve  the  borax  in  250  parts  of  boiling  distilled  water,  and 
filter  while  hot.  Add  the  acid  to  the  hot  filtrate  and  stir.  Set 
aside  in  a  cold  place  for  a  day. 

Collect  the  crystals  on  a  muslin  or  paper  filter  and  wash  them 
with  a  small  quantity  of  cold  distilled  water. 

Re-dissolve  the  washed  crystals  in  200  parts  of  boiling  distilled 
water,  and  set  the  solution  aside  until  quite  cold. 

Place  a  loose  layer  of  clean  cotton  in  the  throat  of  a  glass  fun- 
nel and  collect  the  crystals  upon  it.  Drain  thoroughly.  Transfer 
the  product  to  a  dry  muslin  cloth  or  a  sheet  of  bibulous  white 
paper,  spread  it  out,  and  dry  it  in  a  moderately  warm  place. 

Reaction.     Na2B4O7.ioH2O+2HNO3=4H3BO3 

+2NaN03+5H20. 

Notes.  It  will  be  seen  that  381  parts  of  borax  requires  200 
parts  of  nitric  acid  of  63  per  cent  strength.  A  slight  excess  of 
acid  is,  however,  necessary ;  hence  58  parts  is  ordered  instead  of 
55  for  100  parts  of  borax.  Nitric  acid  is  preferred  to  hydrochloric 
acid  because  sodium  nitrate  is  more  readily  soluble  than  sodium 
chloride.  Sulphuric  acid  is  not  employed  because  it  is  not  so  read- 
ily washed  out. 

The  yield  is  theoretically  about  two-thirds  of  the  weight  of 


ACIDS.  221 

the  borax  used,  but  only  about  50  to  60  per  cent  can  be  obtained 
in  practice. 

Description. — Colorless  or  white,  pearly,  lamellar  crystals,  some- 
what unctuous  to  the  touch;  taste  feebly  acid,  slightly  bitterish. 
Boric  acid  dissolves  in  30  parts  of  water  at  15°  C. ;  in  26  parts  at 
19°  ;  15  parts  at  25°  ;  about  4.75  parts  at  75°  ;  3.55  parts  at  87^5 ; 
and  in  2.97  parts  of  boiling  water. 

Or,  100  parts  of  water  dissolves  3.9  parts  of  boric  acid  at  19° ; 
6.8  parts  at  25°  ;  9.8  parts  at  50° ;  21  parts  at  75° ;  28  parts  at 
87-°5;  and  34  parts  at  100°. 

A  saturated  water-solution  of  boric  acid  at  19°  contains  3.75%  ; 
at  25°  it  contains  6.27%  ;  and  at  the  boiling  point  of  water  25.17 
per  cent. 

It  is  soluble  in  15  parts  of  alcohol  at  15°  according  to  the  U.S.P. 
(According  to  Wittstein  it  is  soluble  in  6  parts  of  alcohol ;  but  ac- 
cording to  the  British  Pharmacopoeia  it  requires  30  parts  of 
alcohol  of  90  per  cent  strength.) 

It  is  soluble  in  about  4  to  5  parts  of  glycerin  at  15°  (in  10  parts 
according  to  the  U.S. P.). 

Crystallised  Boric  Acid. 

Boric  acid  may  be  obtained  in  rather  large,  handsome,  pearly 
crystals  by  the  spontaneous  evaporation  of  a  filtered  solution 
made  of  I  part  of  boric  acid  and  20  parts  of  hot  distilled  water. 
This  solution  should  be  slowly  cooled. 

Handsome  crystals  may  also  be  obtained  by  the  spontaneous 
evaporation  of  a  saturated  alcoholic  solution. 

B or o  glycerin. 
(GLYCERYL  BORATE.    BOROGLYCERIDE.  ) 

Boric  acid,  in  fine  powder 2  parts 

Glycerin  3  parts 

Heat  together  in  a  porcelain  dish  at  about  150°  C.,  stirring 
well,  until  aqueous  vapors  cease  to  be  given  off  and  a  homoge- 
neous, transparent  mass  is  formed,  which  becomes  firm  and  tough 
on  cooling. 


222  ACIDS. 

Reaction.     C3H5(OH)3+H3BO3=C3H5BO3+3H2O. 

Notes.  If  the  materials  are  pure,  and  if  no  foreign  organic 
matter  be  permitted  to  get  into  the  dish,  the  product  will  be  per- 
fectly clear  and  colorless.  The  heat  applied  should  not  be  greater 
than  necessary.  Boroglycerin  is  a  remarkably  tenacious  sub- 
stance, which,  while  warm,  can  be  drawn  into  slender  threads  of 
great  length.  It  is  readily  soluble  in  water,  in  alcohol,  and  in 
glycerin. 

Glyceritum  Boroglycerini;  U.S. 

A  glycerin-solution  of  glyceryl  borate  (boroglycerin  or  boro- 
glyceride)  is  ordered  Jby  the  Pharmacopoeia,  prepared  as  follows: 

Boric  acid,  in  fine  powder , 31  Gm 

Glycerin. 

Heat  46  Gm  of  glycerin  in  a  tared  porcelain  dish  to  not  over 
150°  C. ;  add  the  boric  acid  gradually  and  stir  well.  When  all 
of  the  boric  acid  has  been  added  and  dissolved,  continue  the  heat, 
stirring  constantly  to  prevent  the  formation  of  any  film  on  the 
surface  of  the  mixture,  until  the  weight  of  the  contents  of  the 
dish  shall  have  been  reduced  to  50  Gm.  Then  add  50  Gm  of 
glycerin,  mix  well,  and  transfer  the  product  to  a  suitable  con- 
tainer, which  must  be  tightly  closed. 

Notes.  The  preparation  is  a  perfectly  clear,  colorless,  thick 
liquid.  It  is  hygroscopic. 

CITRIC  ACID. 

ACIDUM    CITRICUM. 
H3C6H507.H20=2IO. 

Contained  in  various  plant  juices,  especially  of  lemons,  limes, 
and  currants.  The  juice  is  allowed  to  ferment  enough  to  decom- 
pose the  sugar.  Then  follows  clarification  with  albumen,  after 
which  the  juice  is  treated  with  prepared  chalk,  and  the  calcium 
citrate  decomposed  with  sulphuric  acid : 

Lemon    juice 800  ml 

Prepared   chalk 45  Gm 

Sulphuric  acid 25  ml 


ACIDS.  223 

Heat  the  lemon  juice  to  the  boiling  point,  and  gradually  add  the 
chalk  until  it  no  longer  causes  effervescence.  Collect  the  deposit 
on  a  muslin  strainer  and  wash  it  with  hot  water  till  the  filtered 
liquid  passes  colorless.  Mix  the  deposited  calcium  citrate  with 
200  ml  of  water,  and  gradually  add  the  sulphuric  acid  previously 
diluted  with  300  ml  of  water.  Boil  gently  for  half  an  hour,  keep- 
ing the  mixture  constantly  stirred.  Separate  the  acid  solution  by 
filtration,  wash  the  insoluble  matter  with  a  little  distilled  water, 
and  add  the  washings  to  the  solution.  Concentrate  this  solution 
to  the  density  of  1.21,  then  allow  it  to  cool,  and  after  twenty-four 
hours  decant  the  liquor  from  the  crystals  of  calcium  sulphate 
which  have  formed,  continue  the  evaporation  of  the  solution  until 
a  pellicle  forms,  and  then  set  aside  to  "cool  and  crystallize.  If 
necessary,  purify  the  acid  by  recrystallization. 

Reaction.  The  free  citric  acid  in  the  lemon  juice  is  neutralized 
by  the  calcium  carbonate,  whereby  calcium  citrate  is  formed : 

2  ( H3C6H507.H20 )  +3CaC03=Cas  ( C6H5O7 )  2+5H2O+3CO2. 

When  the  calcium  citrate  is  treated  with  sulphuric  acid,  the  fol- 
lowing reaction  occurs : 

Ca3  ( CeH607)  2+3H2S04=2H3C6H507+3CaS04. 

Notes.  A  small  amount  of  acid  calcium  citrate  always  remains 
in  the  liquid  after  the  treatment  with  chalk.  This  acid  salt  pre- 
vents the  precipitation  of  coloring  matter,  and  after  the  removal 
of  the  neutral  calcium  citrate,  the  acid  citrate  can  be  decomposed 
by  milk  of  lime,  yielding  normal  citrate. 

The  precipitated  calcium  citrate  is  washed  with  warm  water 
until  the  washings  are  nearly  colorless.  After  cooling,  it  is  de- 
composed by  sulphuric  acid  added  in  excess  to  prevent  the  forma- 
tion of  acid  citrate,  which  would  prevent  crystallization  of  the 
citric  acid.  The  calcium  sulphate  is  washed  and  then  thrown 
away ;  but  the  last  of  the  calcium  sulphate  does  not  separate  until 
the  solution  has  been  evaporated  down  to  1.21  sp.  gr.  The  final 
evaporation  to  crystallization  must  not  be  carried  too  far,  as  the 
free  sulphuric  acid  present  would  then  blacken  the  product  when 
sufficiently  concentrated  to  decompose  the  citric  acid. 

Recrystallization  is  necessary  to  render  the  crystals  colorless 


224  ACIDS. 

and  pure.    Sometimes  the  solution  must  be  decolorized  by  animal 
charcoal. 

Description. — Colorless,  translucent,  prisms  ;  odorless ;  having 
an  agreeable,  purely  acid  taste;  efflorescent  in  warm  air,  and 
deliquescent  when  exposed  to  moist  air. 

Soluble,  at  15°  C.,  in  0.63  part  of  water,  and  in  1.61  parts  of 
alcohol;  in  about  0.4  part  of  boiling  water,  and  in  1.43  parts  of 
boiling  alcohol;  also  soluble  in  18  parts  of  ether. 


HYDRIODIC  ACID. 

ACIDUM     HYDRIODICUM. 

HI=  127.5. 

A  solution  of  hydriodic  acid,  or  ''diluted  hydriodic  acid,"  con- 
taining 10  per  cent  of  hydrogen  iodide,  may  be  prepared  by  a 
process  similar  to  that  prescribed  by  the  Pharmacopoeia  for  mak- 
ing the  syrup  with  the  exception  that  water  is  added  instead  of 
the  same  quantity  of  syrup,  at  the  end. 

Diluted  hydriodic  acid  is  a  colorless,  odorless  liquid  of  acid 
taste.  It  should  be  kept  in  glass-stoppered  bottles,  entirely  filled 
and  placed  in  a  cool,  dark  place.  It  is  very  unstable ;  but  may  be 
preserved  for  a  time  with  the  aid  of  sugar. 

The  official 

Syrup  of  Hydriodic  Acid 
is  made  as  follows : 

Potassium  iodide 13  Gm 

Potassium    hypophosphite I   Gm 

Tartaric  acid 12  Gm 

Water 15  ml 

Diluted  alcohol. 
Syrup. 

Dissolve  the  two  potassium  salts  in  water,  and  the  tartaric  acid 
in  25  ml  of  diluted  alcohol.  Mix  the  two  solutions  in  a  vial, 
shake  it  thoroughly,  and  place  it  in  ice-water  for  half  an  hour, 
occasionally  shaking.  Then  filter  the  mixture  through  a  small, 


ACIDS. 

rapidly-acting,  white  filter,  and  carefully  wash  the  vial  and  filter 
with  diluted  alcohol,  until  the  filtrate  ceases  to  produce  more 
than  a  faint  cloudiness  when  a  drop  or  two  is  allowed  to  fall  into 
silver  nitrate  test-solution.  Reduce  the  filtrate,  by  evaporation  in 
a  tared  capsule,  on  a  water-bath,  to  50  Gm,  and  mix  it,  when 
cold,  with  enough  syrup  to  make  the  product  weight  1000  Gm. 

Keep  it  in  small  filled  glass-stoppered  bottles  in  a  cool,  dark 
place. 

Notes.  The  hypophosphite  is  added  to  form  some  hypophos- 
phorous  acid  which  tends  to  preserve  the  product. 

Description. — A  clear,  colorless,  odorless,  syrupy  liquid  contain- 
ing about  i  per  cent  by  weight  of  absolute  hydrogen  iodide,  or 
about  1.3  Gm  in  each  100  ml.  Its  sp.  w.  is  about  1.313. 

When  it  becomes  discolored  from  free  iodine  it  should  be  re- 
jected. A  darker  color  than  a  pale  straw  is  inadmissible. 


DILUTED  HYDROBROMIC  ACID. 

ACIDUM  HYDROBROMICUM  DILUTUM. 

HBr==8i. 

Sulphuric  acid 14  parts 

Potassium  bromide 12  parts 

Distilled  water,  sufficient. 

Put  two  parts  of  the  water  in  a  porcelain  dish  capable  of  hold- 
ing about  32  parts  ;  stir  the  water  into  a  rapid  rotary  motion ;  then 
add  the  sulphuric  acid  slowly  and  in  a  thin  stream,  continuing  the 
stirring  with  a  glass  rod. 

Put  the  potassium  bromide,  previously  reduced  to  coarse  pow- 
der, in  the  dish;  add  13  parts  of  water,  heat  the  mixture  by  a 
sand-bath  until  the  salt  is  dissolved,  and  while  the  solution  is  still 
hot  add  to  it  the  sulphuric  acid  mixture,  stirring  briskly.  Set 
aside  for  twenty- four  hours. 

Decant  the  acid  supernatant  liquid  (hydrobromic  acid)  from  the 
crystals  of  potassium  sulphate,  and  pour  it  into  a  suitable  distilling 
flask.  Wash  the  crystals  with  a  little  cold  water,  and  add  these 
washings  to  the  liquid. 

Provide  the  flask  with  a  perforated  stopper  and  safety  tube; 

Vol.    11—15 


226  ACIDS. 

connect  it  with  a  well  cooled  receiver,  and  distill  nearly  to  dry- 
ness.  Assay  the  distillate  and  dilute  it  with  enough  distilled  water 
to  make  the  final  product  contain  10  per  cent  of  hydrogen  bro- 
mide. 

Reaction.     2KBr-j-H2SO4=K2SO4+2HBr. 
Other  Methods. 

Hydrobromic  acid  may  also  be  made  from  bromine  and  hydro- 
gen sulphide  as  described  under  the  title  of  Ammonium  Bromide, 
and  from  potassium  bromide  with  tartaric  acid  as  follows : 

.  C  0  Potassium  bromide 4  parts 

Tartaric  acid 5  parts 

Distilled  water 25  parts 

~°   • 

Dissolve  the  bromide  and  the  acid,  separately,  each  in  12.50 
parts  of  distilled  water.  Filter  the  solutions.  Mix  them,  stirring 
well.  Filter  out  the  cream  of  tartar.  Assay  the  solution  and 
adjust  its  strength  to  10  per  cent. 

Valuation.  To  neutralize  8.08  Gm  of  diluted  hydrobromic 
acid  (10  per  cent  of  HBr)  requires  10  ml  of  normal  solution  of 
potassium  hydroxide.  Each  ml  of  the  volumetric  test  solution 
corresponds  to  i  per  cent  of  hydrogen  bromide.  Phenolphtalein 
is  the  indicator  used. 

One  ml  of  normal  solution  of  KOH  is  the  equivalent  of  0.08076 
Gm  of  absolute  HBr. 

Description. — A  clear,  colorless,  odorless,  strongly  acid  liquid 
having  a  sp.  w.  of  about  1.077  at  15°. 

It  is  to  be  kept  in  glass-stoppered  bottles  in  a  cool,  dark  place. 


HYDROCHLORIC   ACID. 

ACIDUM    HYDROCHLORICUM. 

HC1=36.4. 

Hydrochloric  acid  is  prepared  by  double  decomposition  between 
sodium  chloride  and  sulnhuric  acid : 


ACIDS.  227 

NaCl+H2SO4=NaHSO4+HCl;  and 
NaCl+NaHS04=Na2S04+HCl. 

The  hydrochloric  acid  of  the  Pharmacopoeia  of  the  United 
States  C9ntains  31.9  per  cent  of  HC1  and  has  a  sp.  w.  of  about 
1.163  at  15°.  It  is  a  colorless,  corrosive,  fuming  liquid,  of  suffo- 
cating- acid  odor,  and  intensely  acid  taste  and  reaction.  When 
diluted  with  twice  its  volume  of  water  the  acid  ceases  to  give  off 
fumes  and  becomes  odorless. 

The  acid  styled  "C.P."  in  the  trade  usually  holds  the  pharmaco- 
poeical  tests  as  to  purity. 

The  customary  "five-pint-acid-bottles"  hold  six  pounds  of  hy- 
drochloric acid. 

The  white  vapors  given  off  by  strong  hydrochloric  acid  are  due 
to  the  difference  in  the  proportion  of  moisture  contained  in  the 
air  and  in  the  acid  as  well  as  to  the  formation  of  ammonium 
chloride  when  the  acid  vapors  meet  ammonia  in  the  atmosphere. 

Valuation.  To  neutralize  3.64  Gm  of  official  hydrochloric  acid, 
diluted  with  10  ml  of  water,  should  require  31.9  ml  of  normal 
solution  of  potassium  hydroxide.  Each  ml  of  this  volumetric 
solution  corresponds  to  i  per  cent  of  absolute  HC1.  Phenolph- 
talein  is  used  as  the  indicator. 

One  ml  of  normal  solution  of  potassium  hydroxide  is  the 
equivalent  of  0.03637  Gm  of  absolute  HC1. 

Action  on  metals.  Dissolves  iron  and  zinc  readily ;  it  also  acts 
on  nickel  and  aluminum,  and  warm  acid  attacks  tin.  Hydro- 
chloric acid  does  not  attack  platinum,  gold,  silver,  mercury,  lead, 
copper,  arsenic,  antimony  and  bismuth. 

Diluted  Hydrochloric  Acid. 

Hydrochloric   acid 100  Gm 

Distilled    water 219  Gm 

Mix  them.     Keep  the  product  in  glass-stoppered  bottles. 

Diluted  hydrochloric  acid  contains  10  per  cent  of  hydrogen 
chloride. 

Specific  gravity:  about  1.050  at  15°  C. 

It  does  not  fume  in  the  air,  and  is  without  odor,  but  otherwise 
it  corresponds  in  properties  to  hydrochloric  acid. 

To  neutralize  3.64  Gm  of  diluted  hydrochloric  acid  should  re- 


228  ACIDS. 

quire  10  ml  of  normal  potassium  hydroxide  solution  (each  ml 
corresponding  to  I  per  cent  of  the  absolute  acid),  phenolphtalein 
being  used  as  indicator. 

DILUTED  HYDROCYANIC  ACID. 

ACIDUM   HYDROCYANICUM   DILUTUM. 


Must  contain  just  2  per  cent  of  hydrogen  cyanide: 

Potassium  f  errocyanide,  in  coarse  powder ....   4  parts 
Sulphuric  acid 3  parts 

The  apparatus  necessary  consists  of  'a  long-necked  flask  fitted 
with  a  twice  perforated  stopper  carrying  a  safety  tube  and  the 
bent  tube  connecting  the  flask  with  a  Liebig's  or  other  suitable 
condenser,  the  exit  tube  of  which  should  dip  into  the  liquor  in 
the  receiver.  The  receiver  should  be  tared,  should  be  large 
enough  to  permit  the  final  adjustment  of  strength  without  a 
change  of  vessel,  and  should  be  placed  in  broken  ice  or  ice-water. 

Put  1 6  parts  of  distilled  water  in  the  receiver. 

The  ferrocyanide  is  to  be  dissolved  in  20  parts  of  water  and 
then  introduced  into  the  flask.  The  acid  is  diluted  by  adding  it 
gradually  to  twice  its  weight  of  water,  and,  after  connecting  the 
whole  apparatus  together  properly  and  making  all  the  joints  tight, 
the  cold  diluted  acid  is  poured  in  through  the  safety  tube.  Heat 
the  flask  on  a  sand-bath  to  the  boiling  point,  and  continue  apply- 
ing a  moderate  heat  until  there  is  but  little  liquid  mixed  with  the 
saline  mass  remaining  in  the  flask.  Then  detach  the  receiver  and 
assay  a  sufficient  portion  of  the  contents.  The  distillate  is  then 
to  be  diluted  with  distilled  water  so  that  the  finished  product  will 
have  the  required  strength  (2  per  cent). 

Reaction.     2K4FeCy6+3H2SO4=3K2SO4 

+K2Fe2Cy6+6HCy. 

Notes.  A  flask  is  used  instead  of  a  retort  because  more  con- 
venient. If  a  retort  be  used  it  should  be  directed  upward  to  pre- 
vent contamination  of  the  distillate  from  spurting. 

The  heat  required  is  not  far  above  the  boiling  point  of  water. 


ACIDS.  229 

A  sand-bath  is  to  be  preferred  to  naked  flame  to  avoid  bumping. 
The  reaction  should  be  slow  and  regular,  which  requires  rather 
diluted  solutions^  as  here  indicated,  and  sufficient  control  of  the 
heat.  But  too  great  dilution  favors  bumping. 

When  the  process  is  carried  out  as  directed  in  the  formula  above 
stated,  the  distillate  will  contain  about  3  to  4  per  cent  of  hydro- 
cyanic acid. 

The  official  method  of  ascertaining  the  strength  of  the  distillate 
is  as  follows : 

Mix  0.27  Gm  of  the  distillate  in  a  flask  of  100  Cc.  capacity  with 
sufficient  water  and  magnesia  to  make  an  opaque  mixture  of  about 
10  Cc.  Now  add  two  or  three  drops  of  potassium  chromate  test 
solution,  and  then  run  in  from  a  burette  a  quantity  of  decinormal 
volumetric  silver  nitrate  solution  just  sufficient  to  produce  a  red 
tint,  which  does  not  disappear  on  shaking.  Each  ml  used  of  the 
silver  solution  corresponds  to  I  per  cent  of  absolute  hydrocyanic 
acid. 

Multiply  the  per  cent  thus  found  by  the  total  weight  of  the  dis- 
tillate in  grams  and  divide  the.  product  by  2 ;  the  quotient  shows 
the  total  grams  of  2  per  cent  acid  which  can  be  made  from 
the  whole  amount  of  the  distillate.  Therefore,  the  difference  be- 
tween the  weight  of  the  distillate  obtained  and  the  weight  of  the 
finished  product  which  it  will  make  will  be  the  quantity  of  dis- 
tilled water  to  be  added. 

For  example,  if  we  have  837  Gm  of  distillate  of  3.6  per  cent 
strength  we  would  add  669.6  Gm  of  distilled  water  to  the  837  Gm 
of  distillate,  thus  obtaining  1506.6  Gm  of  final  product,  because — 

3-6X837 
=1506.6. 


After  dilution  the  product  should  be  again  assayed,  when  1.35 
Gm  of  the  preparation  should  require  10  ml  of  the  decinormal  vol- 
umetric silver  nitrate  solution  for  complete  precipitation. 

Diluted  hydrocyanic  acid  always  sustains  loss  of  hydrogen  cya- 
nide in  handling  it.  This  weakening  of  the  acid  is  appreciable  in 
filling  it  in  small  bottles,  and  as  it  must  be  kept  in  small  bottles 
to  avoid  too  great  and  frequent  exposure  to  air  in  using,  it  may  be 
well  to  make  the  product  about  2.1  instead  of  2  per  cent  strength 
to  insure  that  the  bottled  acid  may  be  slightly  above  2  per  cent 


230  ACIDS. 

immediately  after  bottling,  and  not  much  below  2  per  cent  before 
consumed  in  dispensing. 

This  preparation  is  frequently  used  in  extremely  critical  cases 
and  it  must,  therefore,  be  absolutely  reliable.  It  should  accord- 
ingly be  tested  from  time  to  time  and  thrown  away  when  no 
longer  of  proper  strength. 

Official  Alternate  Process. 

The  Pharmacopoeia  also  gives  an  easily  performed  process  for 
the  extemporaneous  preparation  of  diluted  hydrocyanic  acid, 
which  is  as  follows: 

Silver  cyanide    6   parts 

Hydrochloric  acid 5  parts 

Distilled  water 55  parts 

Mix  these  ingredients  in  a  glass-stoppered  bottle,  adding  the 
cyanide  last,  and  shake  well.  When  the  precipitate  has  subsided, 
pour  off  the  clear  liquid,  which  will  be  the  finished  product,  con- 
taining 2  per  cent  of  HCy. 

Reaction.     AgCy+HCl=AgCl+HCy. 
Another  Method. 

Diluted  hydrocyanic  acid  may  also  be  conveniently  made  from 
potassium  cyanide  with  tartaric  acid: 

KCN+H2C4H4O6=KHC4H4O6+HCN. 

It  will  be  seen  from  this  equation  that  65  parts  of  dry  potas- 
sium cyanide  and  150  parts  of  tartaric  acid  will  furnish  27  parts  of 
HCN.  Hence  the  following  formula  may  be  used : 

Potassium  cyanide 22  parts 

Tartaric  acid 50  parts 

Distilled  water. 

Dissolve  the  cyanide  and  the  tartaric  acid,  separately,  each  in 
200  parts  of  distilled  water.  Add  the  solution  of  tartaric  acid  to 
the  other,  stirring  well.  Filter  out  the  precipitated  cream  of  tar- 
tar. Assay  the  filtrate  and  add  enough  distilled  water  to  make 
the  product  contain  exactly  2  per  cent  of  HCN. 


ACIDS.  231 

Theoretically  the  quantity  of  product  obtained  from  these  pro- 
portions should  be  450  parts. 

The  diluted  hydrocyanic  acid  prepared  in  this  way  may  contain 
in  solution  a  minute  amount  of  tartaric  acid  and  of  cream  of 
tartar. 

Description. — Diluted  hydrocyanic  acid  is  a  colorless  liquid  of  a 
strjng  and  characteristic  odor  and  taste,  resembling  those  of 
bitter  almonds  wetted  with  water,  or  of  volatile  oil  of  bitter  al- 
mond. But  as  it  is  extremely  poisonous  it  is  dangerous  to  taste 
or  to  smell  it  without  first  diluting  it  considerably. 

Preservation.  Diluted  hydrocyanic  acid  frequently  undergoes 
some  change  by  which  a  dark  colored  deposit  is  formed  in  it.  Ac- 
cording to  Squibb,  it  may  turn  "nearly  as  black  as  dilute  ink" 
within  a  year  and  a  half,  if  kept  in  glass-stoppered  bottles,  and 
this  change  does  not  occur  when  the  acid  is  put  up  in  corked  vials. 
The  action  which  the  acid  thus  appears  to  have  upon  the  ground 
surface  of  glass  has  not  been  explained. 

The  preparation  should  always  be  kept  in  a  cool,  dark  place. 


DILUTED   HYPOPHOSPHOROUS  ACID. 

ACIDUM   HYPOPHOSPHOROSUM  DILUTUM. 

HPO2H2=:66. 

Calcium  hypophosphite   17  parts 

Oxalic  acid   13  parts 

Dissolve  the  hypophosphite  in  100  parts  of  distilled  water,  and 
the  oxalic  acid  in  50  parts.  Filter  both  solutions.  Add  the  so- 
lution of  oxalic  acid  to  .the  solution  of  calcium  hypophosphite, 
stirring  well.  Filter.  Wash  the  calcium  oxalate  on  the  filter 
with  distilled  water  and  mix  the  washings  with  the  filtrate. 
Evaporate  the  liquid  to  132  parts. 

Reaction. 
Ca(PO2H2)2+H2C2O4.2H2O 

=CaC2O4+2HPO2H2+2H2O. 


232  ACIDS. 

Notes.     The   product  contains    10  per  cent  of  HPO2H2.     It 
must  be  kept  in  a  glass-stoppered  bottle. 


LACTIC    ACID. 

ACIDUM    LACTICUM. 

HC3H5O3=90. 
Milk-sugar  yields,  by  fermentation,  lactic  acid 


Several  other  organic  substances,  as  dextrin,  glucose,  etc.,  are 
also  capable  of  undergoing  lactic  fermentation. 

When  a  mixture  of  100  parts  of  sugar  dissolved  in  sufficient 
water  to  yield  a  solution  of  about  1.06  sp.  gr.,  with  8  to  10 
parts  of  old  cheese,  and  50  parts  of  prepared  chalk,  is  exposed 
for  several  weeks  to  a  moderate  heat,  such  as  is  afforded  in  a 
sunny  place  in  the  summer,  calcium  lactate  is  formed  which  is 
found  crystallized  in  the  liquid.  The  lactate  of  calcium  is  recrys- 
tallized,  if  necessary,  and  decomposed  by  sulphuric  acid,  yielding 
lactic  acid  and  calcium  sulphate. 

Lactic  acid  is  also  prepared  from  milk-sugar  and  skimmed 
milk,  a  mixture  of  300  Gm  of  milk-sugar  and  4  liters  of  milk  be- 
ing exposed  to  a  temperature  of  20°  to  30°  C,  and  the  acid 
neutralized  from  time  to  time  with  sodium  bicarbonate,  until  the 
lactic  fermentation  ceases.  The  solution  of  sodium  lactate  is 
then  evaporated  to  a  syrupy  consistence,  dissolved  in  alcohol, 
and  decomposed  by  sulphuric  acid,  after  which  the  lactic  acid  is 
neutralized  with  chalk,  and  the  lactate  of  calcium  in  turn  de- 
composed to  obtain  a  purer  product.  (See  also,  Ferrous 
Lactate). 

Description.  —  The  lactic  acid  of  the  American  Pharmacopoeia 
contains  75  per  cent  of  absolute  lactic  acid  (HC3H5O3)  and  25 
per  cent  of  water.  It  is  a  colorless,  syrupy  liquid,  without  odor, 
and  of  a  pure  acid  taste.  Absorbs  water  on  exposure  to  moist 
air.  Sp.  w.  about  1.213.  Miscible  with  water,  alcohol  and 
ether  in  all  proportions. 

Valuation.       To     neutralize    4.5    Gm    of     lactic     acid     75% 


ACIDS.  233 

strength)    requires  37.5  ml    of  normal  solution  of  KOH.     The 
indicator  used  is  phenolphtalein. 


NITRIC   ACID. 

ACIDUM    NITRICUM. 

HNO3= 63. 

To  obtain  hydrogen  nitrate,  potassium  or  sodium  nitrate  is 
decomposed  by  hydrogen  sulphate : 

KNO3+H2SO4=KHSO4+HNO3, 

or 
2NaNO3+H2SO4=Na2SO4+2HNO3. 

Theoretically,  101  parts  of  potassium  nitrate  yield  63  parts  of 
HNO3,  corresponding  to  about  92  parts  of  the  official  nitric  acid 
(68  per  cent  HNO3).  The  potassium-hydrogen  sulphate  does 
not  decompose  potassium  nitrate  until  the  temperature  is  so  high 
as  to  decompose  the  nitric  acid ;  hence  it  requires  twice  as  much 
sulphuric  acid  to  make  nitric  acid  from  potassium  nitrate  as  it 
does  to  make  the  same  quantity  of  nitric  acid  from  sodium  nitrate, 
which  is  decomposed  by  sodium-hydrogen  sulphate.  The  pro- 
portions to  be  used  are,  therefore,  1010  parts  of  potassium  nitrate 
and  980  parts  of  H2SO4  (corresponding  to  1020  parts  of  96  per 
cent  sulphuric  acid)  ;  or  850  parts  of  sodium  nitrate  and  510  parts 
of  concentrated  sulphuric  acid. 

If  sodium  nitrate  be  used,  the  sulphuric  acid  must  be  diluted 
with  one-fourth  its  weight  of  water  to  prevent  foaming.  This 
foaming  is  caused  by  the  abstraction  of  water  from  the  nitric  acid 
by  the  sodium-hydrogen  sulphate,  which  results  in  the  decompo- 
sition of  the  acid. 

By  using  enough  sulphuric  acid  to  obtain  a  residue  of  acid  sul- 
phate, the  reaction  can  be  effected  at  a  lower  temperature  than  if 
the  minimum  quantity  be  employed,  and  there  is  then  less  de- 
composition of  the  nitric  acid.  The  usual  practice  is  to  employ 
about  150  parts  of  concentrated  sulphuric  acid,  diluted  with  38 
parts  of  water,  to  170  parts  of  sodium  nitrate. 

The  ordinary  ''half-gallon  acid  bottle"  holds  about  7  pounds  of 
strong  nitric  acid. 


234  ACIDS. 

Purification.  The  most  common  impurities  in  commercial  nit- 
ric acid  are  H2SO4,  Cl,  N2O4,  and  iron  nitrate.  The  chlorine 
is  derived  from  the  chlorides  in  the  nitrates  employed.  Chili  salt- 
peter also  contains  sodium  iodide,  which  gives  rise  to  contamina- 
tion with  iodine  chloride.  The  iron  comes  from  the  iron  cylinders 
in  which  the  distillation  is  conducted  in  the  manufacture  of  nitric 
acid  on  a  large  scale.  Absolute  nitric  acid  (1.52  sp.  gr.)  does 
not  attack  metallic  iron,  and  the  strong  acid  generated  in  the 
iron  cylinders  attacks  the  metal  but  little.  Hence  iron  cylinders 
can  be  used.  The  yellow  or  reddish  color  of  crude  strong  nitric 
acid  is  due  mostly  to  nitrogen  tetroxide,  N2O4.  This  impurity 
may  be  removed  by  heating  the  acid  to  about  80°  to  90°  C, 
whereby  it  is  driven  off. 

The  purification  of  nitric  acid  is  effected  on  a  large  scale  by 
re-distillation  from  glass  retorts.  The  first  portion  distilling  over 
contains  the  nitrogen  oxide,  chlorine  and  iodine.  As  soon  as  the 
distillate  is  colorless  and  free  from  chlorine,  the  receiver  is 
changed,  and  the  distillation  continued  until  about  one-eighth 
remains.  To  fix  the  sulphuric  acid  in  the  crude  nitric  acid,  a 
little  potassium  nitrate  is  added  before  the  distillation. 

Pure  nitric  acid  is  made  directly  from  pure  potassium  nitrate 
and  pure  sulphuric  acid. 

Description. — A  colorless,  fuming  liquid,  of  suffocating  odor; 
extremely  corrosive.  Sp.  w.  about  1.414  at  15°.  Contains  68 
per  cent  of  HNO3. 

The  acid  which  manufacturers  designate  as  "C.  P."  usually 
satisfies  the  pharmacopceial  requirements. 

Valuation.  To  neutralize  3.145  Gm  of  the  official  nitric  acid 
requires  34  ml  of  normal  solution  of  potassium  hydroxide. 
Each  ml  of  this  volumetric  solution  corresponds  to  2  per  cent 
of  absolute  HNO3.  Phenolphtalein  is  the  indicator  used. 

One  ml  of  normal  potassium  hydroxide  solution  is  the  equival- 
ent of  0.06289  Gm  of  HNO3. 

Action  on  metals.  Gold,  platinum,  iridium,  rhodium,  and 
chromium  are  not  affected  by  nitric  acid.  Iron,  lead  and  silver  are 
scarcely  attacked  by  concentrated  nitric  acid,  but  diluted  nitric 
acid  dissolves  them.  Antimony,  tin  and  tungsten  are  oxidized 
but  not  dissolved.  Mercury,  silver  and  bismuth  dissolve  readily, 


ACIDS.  235 

especially  in  warm  nitric  acid,  with  the  evolution  of  nitric  oxide 
(NO)  which,  in  contact  with  the  air,  at  once  oxidizes  to  nitro- 
gen tetroxide  (N2O4),  which  appears  as  red  fumes. 

Diluted  Nitric  Acid. 

Nitric  acid 100  Gm 

Distilled  water. 580  Gm 

Mix  them.  Keep  the  product  in  dark  amber-colored,  glass- 
stoppered  bottles. 

Diluted  nitric  acid  contains  10  per  cent,  by  weight,  of  absolute 
nitric  acid. 

Specific  gravity:   about  1.057  at  I5°  C. 

To  neutralize  6.29  Gm  of  diluted  nitric  'acid  should  require 
10  ml  of  normal  solution  of  potassium  hydroxide  (each  ml  cor- 
responding to  i  per  cent  of  absolute  acid),  phenolphtalein  being 
used  as  indicator. 


NITROHYDROCHLORIC   ACID. 

ACIDUM    NITROHYDROCHLORICUM. 

Nitric  acid 18  ml 

Hydrochloric  acid 82  ml 

Mix  the  acids  in  a  large  glass  beaker,  and,  when  efTesvescence 
has  ceased,  pour  the  mixture  into  a  glass-stoppered  bottle,  which 
should  not  be  more  than  half  filled.  Keep  it  in  a  cool,  dark  place. 

Reaction.     NHO8+3HC1=NOC1+2H2O+2C1. 

Notes.  When  strong  nitric  and  hydrochloric  acids  are  mixed 
both  decompose,  and  free  chlorine  is  formed  in  the  liquid,  which, 
therefore,  is  capable  of  dissolving  gold,  and  has  long  been  known 
under  the  name  of  "aqua  regia."  The  medicinal  value  of  the 
preparation  also  depends  upon  the  free  chlorine  (and  nitrosyl 
chloride)  it  contains. 

The  effervescence  which  always  takes  place  should  be  allowed 
to  cease  before  the  product  is  bottled,  the  acids  should  be  cold 
when  mixed,  and  the  finished  preparation  should  be  kept  in  a  cool 
place. 


236  ACIDS. 

The  pharmacopceial  direction  to  keep-  it  in  bottles  not  more 
than  half  rilled  is  intended  to  prevent  the  possible  bursting  of  the 
bottle  should  the  evolution  of  gas  not  have  been  completed  before 
it  was  bottled. 

Care  must  be  exercised  in  handling  this  acid.  Chemical  action 
must  be  completed  before  it,  or  any  mixture  containing  it,  should 
be  dispensed.  When  mixtures  of  nitrohydrochloric  acid  with 
organic  substances  have  been  made  explosions  have  happened  a 
short  time  after  they  had  been  bottled. 

Description. — A  golden-yellow  fuming  and  extremely  corrosive 
liquid,  having  a  strong  odor  of  chlorine  and  a  strongly  acid  re- 
action. Readily  dissolves  gold  leaf. 

Diluted  Nitrohydrochloric  Acid. 

Nitric  acid 40  ml 

Hydrochloric  acid 180  ml 

Distilled  water 780  ml 

Mix  the  acids  in  a  capacious  glass  vessel,  and,  when  efferves- 
cence has  ceased,  add  the  distilled  water.  Keep  the  product  in 
dark  amber-colored,  glass-stoppered  bottles,  in  a  cool  place. 

Description. — A  colorless  or  pale  yellowish  liquid,  having  a  faint 
odor  of  chlorine,  and  a  very  acid  taste. 


OLEIC   ACID. 

ACIDUM    OLEICUM. 

HC18H3302=282. 

Impure  oleic  acid,  known  as  "red  oil/'  is  obtained  as  a  by- 
product in  the  manufacture  of  candles.  Fats  consist  of  olein, 
palmitin  and  stearin,  which  are  the  glycerides  of  oleic,  palmitic 
and  stearic  acids. 

The  solid  fatty  acids  (palmitic  and  stearic  acids)  are  separated 
for  use  in  making  candles,  and  the  residue,  called  "red  oil,"  is 
crude  oleic  acid,  which  still  contains  some  of  the  solid  acids 
named. 


ACIDS.  237 

This  red  oil  is  purified  by  exposing  it  to  a  temperature  of  about 
4°. 5  C.  when  the  stearic  and  palmitic  acids  contained  in  it  solidify 
and  are  removed  by  pressing  and  straining,  after  which  the  crude 
acid  is  shaken  with  sulphurous  acid,  washed,  and  filtered. 

The  product  is  far  from  being  chemically  pure,  but  is  suf- 
ficiently pure  for  pharmaceutical  and  medicinal  uses. 

Description. — A  pale  yellow,  or  light  sherry-colored,  nearly 
inodorous  and  tasteless,  oily  liquid,  of  neutral  or  but  faintly  acid 
reaction.  Exposed  to  the  air  it  darkens,  becoming  brown,  and 
assumes  a  decidedly  acid  reaction.  Sp.  gr.  0.860  to  0.890.  In- 
soluble in  water  but  readily  soluble  in  alcohol,  chloroform  and 
ether. 


OXALIC   ACID. 

ACIDUM    OXALICUM. 

H2C,O4.2H2O=i26. 

Oxalic  acid  occurs  in  many  plants  in  the  form  of  oxalates  of 
calcium  and  potassium.  It  is,  however,  manufactured  by  heating 
sugar,  starch,  gum,  saw-dust,  or  other  organic  matters  with  nitric 
acid,  or  with  alkali  hydrates.  The  most  common  process  of 
manufacture  consists  in  heating  a  pasty  mixture  of  saw-dust  and 
solution  of  soda  and  potassa  at  204°. 5  C.  for  an  hour  or  two. 
The  dried  mass  contains  28  to  30  per  cent  of  oxalic  acid  as 
oxalates;  by  washing  with  sodium  carbonate  solution,  the  potas- 
sium oxalate  is  decomposed,  leaving  all  of  the  oxalic  acid  in 
the  form  of  sodium  oxalate,  the  potassium  carbonate  being  re- 
moved. The  sodium  oxalate  is  then  treated  with  calcium  hydrate, 
whereby  calcium  oxalate  and  sodium  hydrate  are  produced.  The 
calcium  oxalate  is  then  decomposed  by  sulphuric  acid,  and  the 
oxalic  acid  purified  by  re-crystallization.  The  yield  of  oxalic 
acid  equals  about  one-half  of  the  weight  of  the  saw-dust  used. 

Description. — Colorless  or  white  prisms,  readily  soluble  in  water 
and  alcohol.  It  has  a  strong  acid  taste,  and  is  a  powerful  poison 
in  large  doses  because  so  corrosive. 

Pure  oxalic  acid  volatilizes  on  platinum  without  residue. 


238  ACIDS. 

Purified  Oxalic  Acid. 

Commercial  oxalic  acid 1000  parts 

Hydrochloric  acid  (3i.9%HCl) 300  parts 

Water. 

Put  the  oxalic  acid  in  a  porcelain  dish  and  add  700  partso 
hot  water.  Boil  for  a  few  minutes.  Let  it  settle.  Decant  the 
solution  while  still  hot  from  the  undissolved  portion  (which  con- 
sists mostly  of  oxalates  and  may  be  reserved  for  further  treat- 
ment, if  profitable).  -Add  the  hydrochloric  acid  to  the  hot  so- 
lution obtained.  Stir  well.  Cool  rapidly,  stirring  the  liquid  to 
get  small  crystals.  Collect  the  crystals  and  wash  the  product 
with  a  very  small  quantity  of  cold  water. 

Recrystallize  the  product  once  or  twice  as   may  be  required.  <£ 

Notes.     The   less   soluble  oxalates   remain  undissolved 
commercial  oxalic  acid  is  treated  with  less  water  than  is  . 

for  complete  solution.     The  remaining  oxalates  are  decomposed^    - 
by  the  hydrochloric  acid,  which  is  used  in  considerable  excessLIri 
It  is  best  not  to  allow  the  oxalic  acid  to  form  large  crystals  from_%   jj  ^  ^ 
the  solution  containing  hydrochloric  acid;  small  crystals  are  more7 
readily  washed  free  from  the  HC1.     Recrystallization  from  a  hdtf ^ 
saturated  solution  is  necessary  to  complete  the  purification,  and^3 
it  may  be  found  necessary  to  repeat  it. 

Pure  oxalic  acid  volatilizes  on  platinum  without  residue. 

PHOSPHORIC   ACID. 

ACIDUM    PHOSPHORICUM. 

H3PO4=98. 

Phosphoric  acid  can  be  made  in  various  ways.  It  is  most  com- 
monly made  from  phosphorus  by  oxidation  with  nitric  acid. 
When  strong  nitric  acid  is  used  the  reaction  is  more  rapid  and 
less  heat  is  then  applied ;  when  the  acid  is  diluted,  the  action  be- 
ing less  violent,  more  heat  is  requisite. 

It  requires  26.9  parts  of  phosphorus  to  make  100  parts  of  the 
official  phosphoric  acid.  The  usual  process  is  as  follows : 

Mix  510  Gm  of  nitric  acid  with  500  ml  of  distilled  water  in  a 
tubulated  retort  capable  of  holding  2,000  ml.  Place  the  retort 


ACIDS.  239 

upon  a  sand-bath,  or  on  a  wire  gauze  support,  connect  it  loosely 
\vith  a  well  cooled  receiver.  Add  80  parts  of  phosphorus.  In- 
sert a  funnel  through  the  tubulus  of  the  retort  and  then  gradually 
apply  heat  until  the  reaction  begins.  Regulate  the  heat  so  as  to 
prevent  the  action  from  becoming  violent,  checking  it,  if  need  be, 
by  the  addition  of  a  little  distilled  water.  Continue  the  digestion 
until  all  the  phosphorus  is  dissolved,  and  return  to  the  retort, 
from  time  to  time,  any  liquid  which  may  collect  in  the  receiver. 

When  all  the  phosphorus  is  dissolved  transfer  the  contents  of 
the  retort  to  a  tared  porcelain  dish,  and  heat  the  liquid  at  a  tem- 
perature of  nearly  but  not  above  190°  C.  until  the  excess  of  nitric 
acid  is  expelled  and  an  odorless,  syrupy  liquid  remains.  Cool 
the  dish  and  contents  and  add  enough  distilled  water  to  make 
total  weight  of  the  product  285  Gm. 

Test  the  product  for  nitric,  phosphorous  and  arsenic  acids,  all 


which  must  be  removed  if  present. 

J  ^^  If  nitric  acid  be  present,  evaporate  the  liquid  until  it  ceases 
^-tb  give  any  further  reaction  for  that  acid  ;  then  let  it  cool  and 
Dilute  it  with  distilled  water  until  the  prescribed  weight  (285 

ftl  &'"-    c§m  )   is  restored. 

i*    Q'*"  * 

rn          p^-j  If   phosphorous  acid  be   found   in   the   phosphoric  acid,   add 
Gm    of  nitric  acid  and  again  heat  the  mixture  until  reactions 


r  phosphorous  and  nitric  acids  cease,  and  restore  the  pre- 
f—  scribed  weight  (285  Gm)  by  dilution  with  distilled  water  as 
before. 

Should  arsenic  be  present,  dilute  the  phosphoric  acid  with 
750  ml  of  distilled  water,  heat  the  liquid  to  about  70°  C.  and 
then  pass  through  it  a  stream  of  hydrogen  sulphide  gas  for  half 
an  hour.  Then  remove  the  heat,  but  continue  passing  hydrogen 
sulphide  through  the  dilute  phosphoric  acid  until  it  becomes  cold. 
Close  the  vessel  tightly,  set  it  aside  for  24  hours,  filter  the  liquid, 
then  heat  the  filtrate  until  all  odor  of  hydrogen  sulphide  has  been 
expelled,  filter  again,  and  finally  evaporate  the  now  purified  phos- 
phoric acid  until  its  weight  is  reduced  to  285  Gm. 

The  product  must  be  tested  as  to  its  strength  in  the  manner 
prescribed  below,  and  diluted  or  concentrated,  as  may  be  required. 

Preserve  the  product  in  glass-stoppered  bottles. 

Reactions.     Probably  first  — 
2P+2HNOS+H20=2H,POS+NO. 


240  ACIDS. 

Then 

3H3P03+2HN03=3H3P04+H20+2NO.    ' 

Notes.  The  phosphorus  used  must  be  free  from  sulphur; 
otherwise  sulphuric  acid  will  be  formed  from  the  latter  and  con- 
taminate the  product.  This  result  might,  however,  be  prevented 
by  using  an  excess  of  phosphorus  so  that  some  of  it  remains  un- 
dissolved,  the  phosphorous  acid  being  oxidized  to  phosphoric  acid 
by  a  fresh  portion  of  nitric  acid  after  removing  the  undissolved 
phosphorus  and  sulphur. 

As  the  phosphorus  fuses  collecting  on  the  bottom  of  the  retort, 
or  flask,  where  it  presents  but  a  limited  surface  of  contact  for 
the  action  of  the  nitric  acid,  the  oxidation  is  slow.  High  heat 
renders  the  action  too  violent,  unless  the  nitric  acid  has  been 
properly  diluted,  as  in  the  usual  process  described  above.  Nitric 
acid  of  i  .20  sp.  gr.  is  considered  most  suitable.  Whenever  the 
reaction  is  from  any  cause  too  violent,  there  is  danger  that  par- 
ticles of  phosphorus  may  be  thrown  to  the  surface  of  the  liquid 
and  ignited,  the  heat  from  the  combustion  fracturing  the  vessel 
and  scattering  the  burning  phosphorus,  the  acid  liquid,  and  the 
red  nitrous  fumes.  The  temperature  need  not  exceed  50°  C. 

A  flask  can  be  used  in  place  of  the  retort,  and  the  heating  can 
be  done  in  a  water-bath.  In  that  case  the  neck  of  the  flask 
should  be  covered  by  a  watch  crystal,  the  convex  side  downward, 
so  that  the  liquid  formed  by  the  condensation  of  the  rising  vapors 
may  run  down  into  the  flask  again.  Should  the  flask  or  retort 
break  from  any  cause  while  undissolved  phosphorus  remains  in 
it,  the  use  of  the  water-bath  instead  of  a  sand-bath  would  prevent 
the  ignition  of  the  phosphorus. 

Should  the  liquid,  after  the  phosphorus  has  been  dissolved, 
contain  both  phosphorous  and  arsenic  acids,  and  should  it  then 
be  concentrated  to  less  than  three  times  the  weight  of  the  phos- 
phorus consumed,  the  phosphorous  acid  may  be  oxidized  by 
the  concentrated  nitric  acid  so  violently  that  the  liquid  froths 
over  the  sides  of  the  dish  unless  a  little  water  is  added.  The 
arsenic  then  separates  as  a  brown  powder  of  reduced  metal. 

If  the  liquid  contains  phosphorous  acid,  but  no  nitric  acid,  the 
phosphorous  acid  may  be  lost  during  the  subsequent  evaporation, 
hydrogen  phosphide  being  formed  unless  nitric  acid  be  added 
to  prevent  it. 


ACIDS.  241 

4H3P03=:H3P+3H3P04. 

The  expulsion  of  the  excess  of  nitric  acid  may  be  known  to  have 
been  accomplished  when  a  piece  of  filter-paper  dipped  in  am- 
monia water  no  longer  gives  off  white  fumes  when  held  over  the 
liquid. 

All  of  the  nitric  acid  must  be  expelled  before  the  liquid  is 
charged  with  hydrogen  sulphide  gas  for  the  purpose  of  remov- 
ing arsenic  present.  Otherwise  sulphur  deposits,  which  is  after- 
wards oxidized  into  sulphuric  acid. 

To  facilitate  the  removal  of  the  nitric  acid,  Professor  Lloyd 
employs  a  little  purified  alcohol,  and  Professor  Markoe  adds  a 
small  amount  of  pure  oxalic  acid. 

The  evaporation  of  the  acid  must  be  done  in  well  glazed  por- 
celain dishes  to  avoid  contamination  with  silicic  acid.  When 
silicic  acid  is  present  in  considerable  quantity  in  concentrated 
phosphoric  acid,  it  separates  in  gelatinous  flocculi  upon  dilution 
after  standing  some  time. 

Other  methods.  Phosphoric  acid  has  also  been  made  from 
phosphorus  by  the  use  of  iodine  or  bromine  and  water.  When 
bromine  is  employed  the  phosphorus  combines  with  it,  forming 
PBr,  and  PBr- ;  the  PBr3  with  3H2O  yields  H3PO3+.3HBr, 
while  the  PBr5  with  4H2O  yields  H3PO4+sHBr;  the  H3PO3 
with  2Br  and  H2O  will  form  H3PO4-f-2HBr.  Thus  ten  mole- 
cules of  HBr  are  formed  simultaneously  with  two  molecules 
of  H3PO4,  these  acids  being  separated  by  distillation  and  both 
utilized.  Analogous  reactions  take  place  when  iodine  or  chlorine 
is  used  instead  of  bromine.  These  processes  are,  however,  dan- 
gerous on  account  of  the  violent  chemical  action  and  the  explo- 
sive character  of  the  compounds  of  phosphorus  with  the  halogens. 

In  other  processes  nitric  acid  is  employed  simultaneously  with 
either  bromine,  or  iodine,  or  both.  The  hydrogen  acid  formed  is 
then  decomposed  by  the  nitric  acid  liberating  the  halogen,  which 
again  acts  upon  a  new  portion  of  the  phosphorus : 

3HBr+HNO3=3Br-f2H2O+NO. 

These  processes  are  also  dangerous.  Markoe's  method  is  prob- 
ably the  least  dangerous  of  all  of  them.  He  mixed  540  parts 
of  water,  90  parts  of  phosphorus,  and  I  part  of  iodine  in  a  stone 

Vol.   11—16 


242  ACIDS. 

jar  placed  in  ice-water;  then  6  parts  of  bromine  dissolved  in 
dilute  hydrobromic  acid  is  very  cautiously  added.  After  the 
reaction  540  parts  of  nitric  acid  is  added.  After  24  hours  the 
phosphorus  is  nearly  or  quite  dissolved ;  if  any  of  it  remains  un- 
dissolved  after  that  period,  heat  may  be  safely  applied  to  hasten 
its  oxidation.  The  iodine,  bromine  and  excess  of  nitric  acid 
are  then  driven  off  by  heat. 

The  slow  oxidation  of  phosphorus  by  moist  air  at  a  low  tem- 
perature has  also  been  practiced. 

Ortho-phosphoric  acid  has  also  been  prepared  by  heating  a 
solution  of  glacial  phosphoric  acid  (metaphosphoric  acid)  in 
water,  the  reactions  being:  2HPO3-f H2O=H4P2O7  (pyrophos- 
phoric  acid),  and  then  H4P2O7+H2O=2H3PO4. 

A  considerable  quantity  of  pyrophosphoric  acid  may,  how- 
ever, remain  undecomposed. 

Amorphous  phosphorus  is  readily  oxidized  by  nitric  acid  with- 
out danger  of  fire. 

The  reaction  begins  after  a  few  hours,  generally  without  the 
application  of  any  heat,  and  having  once  commenced  it  progresses 
very  rapidly.  If  a  capacious  vessel  is  employed,  no  danger  need 
be  apprehended. 

Properties.  An  aqueous  solution  containing  85  per  cent  of 
ortho-phosphoric  acid  and  50  per  cent  of  water.  It  is  a  clear, 
colorless  liquid,  without  odor,  of  a  strongly  acid  taste  and  reaction. 
Sp.  w.  not  less  than  1.710  at  15°.  Its  sp.  vol.  is  0.5848. 

Valuation.  To  neutralize  0.98  Gm  of  official  phosphoric  acid 
(85%)  should  require  17  ml  of  normal  solution  of  potassium 
hydroxide.  Each  ml  of  the  volumetric  test  solution  corresponds 
to  5  per  cent  of  H3PO4.  Phenolphtalein  is  used  as  the  indicator. 
The  phosphoric  acid  should  be  somewhat  diluted  with  water  be- 
fore the  potassium  hydroxide  solution  is  added. 

One  ml  of  normal  solution  cf  potassium  hydroxide  is  the 
equivalent  of  0.0489  Gm  of  H3PO4  when  forming  KoHPO4 
(phenolphtalein  being  then  used  as  an  indicator)  ;  it  is  equival- 
ent to  0.0978  of  H3PO4  when  forming  KH.,PO4  (methyl-orange 
being  the  indicator  used  in  this  test). 


ACIDS.  243 

[K3PO4  shows  an  alkaline  reaction  with  all  color  indicators; 
K2HPO4  is  neutral  to  phenolphtalein  but  alkaline  toward  methyl- 
orange  and  Congo-red;  KH2PO4  gives  an  acid  indicator  with 
phenolphtalein  but  a  neutral  reaction  with  methyl-orange.] 

Diluted  Phosphoric  Acid. 

Phosphoric  acid. 100  Gm 

Distilled  water 750  Gm 

Mix  them.     Keep  the  product  in  well-stoppered  bottles. 

Diluted  phosphoric  acid  contains  10  per  cent,  by  weight,  of 
absolute  H3PO4. 

Specific  gravity:   about  1.057  at  I5°  C. 

4.89  Gm  of  diluted  phosphoric  acid  should  require  for  neutral- 
ization 10  ml  of  normal  potassium  hydroxide  solution  (each 
ml  corresponding  to  I  per  cent  of  the  absolute  acid),  phenol- 
phtalein being  used  as  indicator. 

METAPHOSPHORIC  ACID. 

HP03=8o. 
[Glacial  phosphoric  acid.] 

This  ice-like  solid  is  formed  by  heating  the  ordinary  phos- 
phoric acid  to  redness,  or  by  dissolving  phosphorus  pentoxide  in 
cold  water  and  heating.  As  found  in  commerce  it  usually  con- 
tains much  sodium  phosphate. 

SALICYLIC   ACID. 

ACIDUM    SALICYLICUM. 

HC7H503=i38. 

Methyl  salicylate  exists  in  the  volatile  oil  of  gaultheria,  which 
contains  about  90  per  cent  of  this  compound  ether.  Salicylates 
have  also  been  found  in  sweet  birch  and  in  other  plants.  Salicylic 
acid  is  manufactured  as  follows : 

A  solution  of  sodium  hydroxide  is  saturated  with  phenol,  the 
mixture  evaporated  to  dryness  with  constant  stirring,  and  the 


244  ACIDS. 

residue,  while  still  hot,  is  powdered;  the  powder  is  heated  in  a 
retort  over  an  oil-bath  to  100°  C.  whereby  all  moisture  is  driven 
off;  then  a  current  of  dry  carbonic  acid  gas  is  passed  into  the 
retort  under  slight  pressure,  the  temperature  being  raised  to 
180°  C.,  and  finally  to  220° — 250°  C.  The  residue  now  consists 
of  sodium  carbonate  and  sodium  hydroxide  together  with  sodium 
salicylate ;  it  is  dissolved  in  water,  and  hydrochloric  acid  is  added, 
by  which  the  salicylic  acid  is  precipitated  while  sodium  chloride 
remains  in  solution. 

Reactions. 

C6HBOH+NaOH=C6HBONa+H2O;  then 
C6H5ONa+CO2==NaC7H5O3 ;  and 
NaC7HBO8+HCl=HC7HBO8+NaCl. 

Notes.  Much  depends  upon  a  careful  regulation  of  the  tem- 
perature in  this  process.  Potassium  hydroxide  cannot  be  used  in 
place  of  the  sodium  hydroxide,  the  result  being  then  para-oxy- 
benzoic  acid  instead  of  salicylic  acid.  The  chemical  reactions  in- 
clude also  the  formation  of  "sodium-salicylate  of  sodium," 

NaC7H503+C6H5ONa=NaC7H4  ( Na)  O3+C6H5OH ; 

this  compound  is  decomposed  by  the  HC1  yielding  salicylic  acid 
and  sodium  chloride. 

The  crude  salicylic  acid  is  purified  and  decolorized  by  filtra- 
tion of  its  solution  through  animal  charcoal,  and  repeated  re- 
crystallization.  To  perfectly  remove  the  resinous  impurities, 
dialysation  is  resorted  to. 

When  oil  of  wintergreen  is  treated  with  sodium  hydroxide  and 
the  methyl  salicylate  of  sodium  boiled,  methyl  alcohol  and  so- 
dium salicylate  are  formed. 

Precipitated  salicylic  acid  (amorphous)  is  not  sufficiently  pure 
for  medicinal  uses.  The  crystallized  acid  is  required.  Sublimed 
salicylic  acid  often  has  the  odor  of  phenol,  and  acquires  a  red- 
dish tint  on  exposure  to  air  or  sun  light.  The  purest  acid  is  that 
purified  by  dialysis. 

Description. — Fine,  white,  light,  prismatic,  needle-shaped  crys- 
tals, permanent  in  the  air,  free  from  odor  of  carbolic  acid,  but 


ACIDS.  245 

sometimes  having  a  slight  aromatic  odor,  of  a  sweetish  and 
slightly  acrid  taste  and  an  acid  reaction.  Soluble  in  450  parts 
of  water  and  in  2.4  parts  of  alcohol  at  15°  C. ;  in  14  parts  of 
boiling  water ;  very  soluble  in  boiling  alcohol ;  also  soluble  in 
2  parts  of  ether,  in  2  parts  of  absolute  alcohol ;  in  3.5  parts  of 
amylic  alcohol,  and  in  80  parts  of  chloroform.  When  heated  to 
about  156°  C.  the  crystals  melt;  at  a  higher  temperature  they 
are  volatilized  and  decomposed. 

SULPHURIC   ACID. 

ACIDUM    SULPHURICUM. 

H2SO4=98. 

Crude  or  commercial  sulphuric  acid,  still  often  called  "oil  of 
vitriol,"  is  prepared  from  sulphur  dioxide  (obtained  by  burn- 
ing sulphur  or  iron  pyrites)  by  means  of  nitric  acid  in  the  pres- 
ence of  air  and  moisture  in  lead  chambers.  The 

Reactions  are  as  follows: 
2SO2+2HNO3+H2O=2H2SO4+N2O3 ;  then 
N2O3+2SO2+H2O+O2=2SO2OHNO2 ;  then 
2SO2OHNO2+H2O= 2H2SO4+N2O3. 

As  sulphur  and  iron  pyrites  contain  arsenic  the  crude  acid 
formed  in  the  lead  chambers  is  contaminated  with  arsenic  lead 
and  nitric  acid.  The  lead  sulphate  contained  in  the  acid  pre- 
cipitates when  the  strong  acid  is  diluted  with  more  than  three 
times  its  weight  of  water. 

A  much  purer  acid  is  necessary  for  pharmaceutical  purposes. 
A  process  of  purification  is  as  follows : 

A  mixture  of  300  parts  of  crude  commercial  sulphuric  acid 
and  i  part  of  ammonium  sulphate  is  distilled  from  a  retort  by 
gradually  increased  heat  over  the  naked  fire.  The  mixture  is 
slowly  raised  to  the  boiling  point,  and  the  first  15  parts,  contain- 
ing chiefly  water  and  sulphurous  acid,  are  rejected,  after  which 
the  next  225  parts  are  collected. 

The  object  of  adding  the  ammonium  sulphate  is  to  remove 
nitrogenous  compounds  by  decomposition. 


246  ACIDS. 

Notes.  The  pharmacopoeias  contain  sulphuric  acids  varying  in 
strength  from  92.50  per  cent  to  98  per  cent.  That  of  the  United 
States  Pharmacopoeia  is  required  to  contain  at  least  92.5  per  cent 
of  absolute  acid,  and  in  all  official  formulas  wherever  sulphuric 
acid  is  ordered,  the  quantity  prescribed  is  based  upon  the  assump- 
tion that  the  acid  has  that  strength. 

Sulphuric  acid  is  extremely  corrosive  and  destructive.  It  must 
therefore  be  handled  with  great  caution.  It  reacts  violently  with 
all  volatile  oils  and  with  a  number  of  other  substances.  When  it 
is  mixed  with  water  or  with  alcohol  the  chemical  action  which 
takes  place  causes  a  rapid  and  great  rise  of  the  temperature. 
Hence  the  only  safe  way  to  make  these  mixtures  is  to  add  the 
acid  very  slowly  and  in  a  small  stream  to  the  water  or  the 
alcohol,  stirring  constantly.  It  is  also  recommended  that  a  very 
large  vessel  be  used — one  holding  at  least  three  times  as  much  as 
the  total  quantity  of  mixture  to  be  made,  for  if  the  liquid  should 
become  so  hot  as  to  boil  or  spurt  damage  might  otherwise  result. 

Whenever  it  may  be  necessary  to  add  fuming  sulphuric  acid 
("Nordhausen  acid"),  or  nearly  absolute  sulphuric  acid  to  a 
weaker  sulphuric  acid  in  order  to  produce  a  mixture  of  definite 
strength,  as,  for  instance,  to  make  an  acid  containing  exactly 
98  per  cent  of  absolute  hydrogen  sulphate,  the  stronger  acid 
should  be  added  to  the  weaker.  And  when  a  strong  sulphuric 
acid  is  to  be  diluted  with  a  comparatively  small  amount  of  water, 
the  order  of  mixing  should  be  as  stated  before — the  acid  must 
be  added  to  the  water  and  not  the  water  to  the  acid. 

The  acid  sold  by  manufacturers  and  dealers  under  the  desig- 
nation "chemically  pure"  (C.  P.)  is  generally  sufficiently  pure 
for  pharmaceutical  purposes,  fulfilling  the  requirements  of  the 
Pharmacopoeia. 

Sulphuric  acid  is  customarily  put  up  in  bottles  containing  one, 
or  two,  or  nine  pounds.  The  ordinary  so-called  "five  pint  acid" 
bottle  holds  nine  pounds  of  concentrated  sulphuric  acid. 

Description. — A  colorless,  oily,  odorless,  extremely  corrosive 
liquid.  Sp.  w.  not  less  than  1.835  at  1S°- 

Action  on  metals.  Concentrated  sulphuric  acid  attacks  copper, 
and,  if  hot,  it  also  attacks  mercury,  silver  and  bismuth.  Diluted 
sulpuhric  acid  attacks  and  dissolves  iron,  zinc,  and  nickel,  but 


ACIDS.  247 

does  not  dissolve  platinum,  gold,  silver,  lead,  copper,  mercury, 
aluminum,  arsenic,  antimonv  and  bismuth. 


Diluted  Sulphuric  Acid. 

Sulphuric  acid  (92.5%) 100  parts 

Distilled  water 825  parts 

Pour  the  acid  slowly,  in  a  small  stream,  into  the  distilled  water, 
under  constant  stirring. 

Keep  the  liquid  in  glass-stoppered  bottles. 

Notes.  When  sulphuric  acid  and  water  are  mixed  a  consider- 
able rise  of  the  temperature  and  a  contraction  of  volume  take 
place.  If  the  liquids  are  mixed  too  rapidly,  or  the  water  added 
to  the  acid  instead  of  vice  versa,  the  heat  generated  may  be  so 
great  as  to  cause  serious  accidents  by  violent  boiling  or  spattering. 

The  diluted  sulphuric  acid  obtained  by  the  foregoing  formula 
contains  10  per  cent  of  absolute  H2SO4. 

Fuming  Sulphuric  Acid,  or  Nordhausen  Sulphuric  Acid. — This 
is  a  mixture  of  SO3  and  H2SO4,  or  possibly  H2S2O7.  It  is  also 
called  "pyrosulphufic  acid"  and  "disulphuric  acid."  It  is  made 
by  distilling  ferrous  sulphate  which  has  been  first  dried  to  a  cer- 
tain point : 

4FeSO4+H2O=2Fe2O8+H2S2O7+2SOa. 

Fuming  sulphuric  acid  is  a  thick  liquid,  extremely  corrosive, 
and  gives  off  dense  fumes. 

Haller's  Acid  Drops. 

LIQUOR     ACIDUS     HALLERI. 

This  is  a  mixture  of  equal  parts  by  weight  of  alcohol  and  sul- 
phuric acid.  The  acid  must  be  added  to  the  alcohol  gradually  and 
cautiously,  with  constant  stirring,  in  order  that  the  temperature 
may  not  rise  so  high  as  to  cause  the  liquid  to  boil.  The  liquid 
contains  alcohol,  sulphuric  acid,  ether,  and  ethyl-sulphuric  acid. 
If  the  alcohol  was  pure,  the  preparation  is  colorless. 


248  ACIDS. 

AROMATIC    SULPHURIC   ACID. 

ACIDUM    SULPHURICUM    AROMATICUM U.    S. 

Sulphuric  acid  (92.5%) IOD  ml 

Tincture  of  ginger 5°  m^ 

Oil  of  cinnamon i  ml 

Alcohol,  sufficient. 

Add  the  acid  slowly  and  in  small  stream  to  800  ml  of  alcohol, 
stirring  constantly,  being  careful  not  to  add  the  acid  so  rapidly 
as  to  cause  the  mixture  to  boil.  When  the  mixture  has  cooled 
add  the  tincture  and  the  volatile  oil.  Finally  add  enough  alcohol  to 
make  the  product  measure  1,000  milliliters. 

Keep  it  in  glass-stoppered  bottles. 

Notes.  Aromatic  sulphuric  acid  contains  about  20  per  cent  of 
sulphuric  acid,  chiefly  in  the  form  of  ethyl-sulphuric  acid  or  acid 
ethyl  sulphate.  It  also  contains  some  ether  and  various  other 
products  formed  by  the  chemical  action  of  the  sulphuric  acid  on 
the  other  ingredients. 

Description. — It  is  a  pale  yellowish-brown  liquid  of  aromatic 
and  strongly  acid  taste.  Becomes  darker  by  age  through  the  car- 
bonization of  the  organic  matter  by  the  sulphuric  acid. 

SULPHUROUS    ACID. 

ACIDUM    SULPHUROSUM. 

The  "sulphurous  acid"  of  the  Pharmacopoeia  of  the  United 
States  is  an  aqueous  solution,  representing  8.2  per  cent  of  H2SO3, 
corresponding  to  6.4  per  cent  of  sulphur  dioxide  (SO2). 

It  is  prepared  as  follows : 

Sulphuric  acid. 80  ml 

Charcoal,  in  coarse  powder 20  Gm 

Distilled  water i  liter 

Sodium  carbonate ; .  10  Gm 

Put  the  acid  and  the  charcoal  in  a  flask  of  about  500  ml  ca- 
pacity. Connect  the  flask  by  means  of  bent  glass  tubing  and  per- 
forated rubber  stoppers  with  a  wide  mouthed  bottle  of  about 


ACIDS.  249 

200  ml  capacity,  to  be  used  as  a  wash-bottle  and  for  that  purpose 
one-third  filled  with  water.  The  wash-bottle  is  to  be  fitted  with 
a  rubber  stopper  having  three  perforations — one  for  the  glass 
tube  connecting  it  with  the  flask  used  as  a  generator,  another 
for  a  safety  tube,  and  the  third  for  the  glass  tube  connecting  the 
wash-bottle  with  the  receiver,  which  should  consist  of  a  bottle 
of  about  1.5  liters  capacity  and  containing  i  liter  of  water.  The 
tube  between  the  generator  and  the  wash-bottle,  and  also  the 
safety-tube,  should  reach  nearly  to  the  bottom  of  the  wash-bottle ; 
the  tube  connecting  the  wash-bottle  with  the  receiver  should  end 
just  below  the  stopper  of  the  wash-bottle  above  the  surface  of  the 
wash  water,  and  should  dip  about  three  centimeters  below  the 
surface  of  the  distilled  water  which  is  put  into  the  receiver.  Con- 
nect the  receiver  in  the  same  manner  with  the  second  wid£- 
mouthed  bottle  of  50  ml  capacity  containing  the  sodium  car- 
bonate dissolved  in  30  ml  of  water.  The  joints  between  the 
pieces  of  glass  tubing  should  be  of  soft  rubber.  Having  made 
all  the  joints  tight,  apply  heat  to  the  flask  by  means  of  a  sand- 
bath,  and  continue  the  heating  until  the  evolution  of  gas  has 
nearly  ceased,  keeping  the  receiver  at  or  below  10°  C.  (50°  F.) 
by  means  of  cold  water  or  crushed  ice.  Then  remove  the  re- 
ceiver, shake  the  contents,  and  keep  the  product  in  dark,  amber 
colored,  glass-stoppered  bottles,  completely  filled,  in  a  cool  and 
dark  place. 

Test  of  strength.  If  2  Gm  of  the  sulphurous  acid  be  diluted 
with  25  ml  of  distilled  water  and  a  little  test-solution  of  starch 
added,  it  should  require  not  less  than  40  ml  of  decinormal  test- 
solution  of  iodine  to  produce  a  permanent  blue  color  in  the  liquid, 
which  would  show  the  presence  of  6.4  per  cent  of  SO2  (each  ml 
of  the  iodine  solution  being  required  for  each  0.16  per  cent  of 
SO2  contained  in  the  product). 

Reaction.     4H2SO4+2C=4SO2+2CO2+4H2O. 

Notes.  As  soon  as  the  reaction  ceases  the  wash-bottle  must  be 
at  once  disconnected  from  the  generator;  otherwise  the  vacuum 
produced  in  the  latter  will  cause  the  liquid  in  the  wash-bottle  to 
be  forced  back  into  the  flask,  causing  its  fracture.  The  solution 
of  sodium  carbonate  in  the  end-bottle  is  to  absorb  the  gas  which 
is  not  absorbed  by  the  water  in  the  receiver. 


25O  ACIDS. 

Sulphurous  acid  deteriorates  rather  rapidly  by  oxidation  to 
sulphuric  acid. 

Description. — A  colorless  solution  with  strong  characteristic 
odor  of  burning  sulphur,  and  sharp  acid  taste  and  reaction.  Its 
specific  gravity  is  1.035  at  :50  C. 

Another  Method. 

Sodium  bisulphite, 

Diluted  sulphuric  acid, 

Distilled  water,  of  each  sufficient. 

Introduce  the  sodium  bisulphite  in  a  suitable  roomy  flask  pro- 
vided with  stopper,  safety  tube  and  delivery  tube,  and  connected 
with  a  wash-bottle  containing  some  distilled  water  and,  in  turn, 
connected  with  a  receiving  bottle  containing  cold  distilled  water, 
previously  freed  from  air  by  boiling. 

Add  the  diluted  sulphuric  acid,  a  little  at  a  time,  through  the 
safety  tube,  being  careful  not  to  add  the  acid  too  rapidly  so  as 
tc  cause  a  too  rapid  evolution  of  the  gas. 

When  the  water  in  the  receiving  bottle  has  been  saturated  bot- 
tle the  product. 

Reaction.     2NaHSO3+H2SO4=Na2SO4+2H2O+2SO2. 

Notes.  This  process  is  not  as  economical  as  the  official  method, 
but  it  is  more  convenient  and  may  often  be  found  preferable. 
Theoretically  103.9  Gm  of  sodium  bisulphite  yields  64  Gm  of 
SO2,  or  enough  to  saturate  one  liter  of  water ;  but  allowance 
must  be  made  for  the  SO2  held  in  the  wash-bottle  and  that  re- 
maining in  the  various  parts  of  the  apparatus  so  that  much 
more  than  that  quantity  is  consumed.  The  quantity  of  diluted 
sulphuric  acid  required  is  about  five  times  the  amount  of  so- 
dium bisulphite. 

The  size  of  the  vessels,  the  amount  of  water  in  wash-bottle 
and  receiver,  the  temperature  of  the  water  in  the  receiver,  and 
certain  other  details,  are  indicated  in  the  official  process  already 
described.  The  end  bottle  containing  sodium  carbonate  should 
not  be  omitted. 

Two  receiving  bottles  may  be  alternately  used,  until  the  water 
in  both  shall  have  been  saturated.  Each  bottle  can  then  be  shaken 
occasionally. 


ACIDS.  251 


TARTARIC  ACID. 

ACIDUM    TARTARICUM. 


Tartaric  acid  occurs  in  grapes  and  in  other  fruits,  in  the  form 
of  acid  potassium  tartrate,  from  which  it  is  manufactured. 
The  following  formula  is  based  on  Scheele's  process: 

Cream  of  tartar  ......................  900  Gm 

Prepared  chalk  .......................  250  Gm 

Calcium  chloride  ......................  270  Gm 

Sulphuric   acid  .......................  260  ml 

Distilled  water,  sufficient. 

Boil  the  cream  of  tartar  with  6,500  ml  of  water,  and  gradually 
add  the  chalk,  stirring  constantly.  When  effervescence  has 
ceased,  add  the  calcium  chloride  dissolved  in  800  ml  of  water. 
When  the  calcium  tartrate  has  subsided,  decant  the  liquid,  and 
wash  the  tartrate  with  water  until  tasteless.  Pour  the  sulphuric 
acid,  previously  diluted  with  1,200  ml  of  water,  on  the  calcium 
tartrate,  mix  thoroughly,  boil  for  half  an  hour  with  repeated 
stirring,  and  filter  through  muslin.  Evaporate  the  filtrate  at 
a  low  temperature  until  it  acquires  the  specific  gravity  1.21,  let 
it  cool,  and  then  separate  and  reject  the  crystals  of  calcium  sul- 
phate formed.  Again  evaporate  the  clear  liquid  until  a  pellicle 
forms,  and  then  set  aside  to  cool  and  crystallize.  Lastly,  purify 
the  product  by  re-crystallization. 

Reaction.  2KHC4H4O6+CaCO3  =  CaC4H4O6+K2C4H4O6+ 
H2O+CO2,  and  K2C4H4O6+CaCl2=CaC4H4O6-f  2KC1  ;  finally, 
CaC4H4O6+H2SO4=H2C4H4O6-fCaSO4. 

Notes.  Tartaric  acid  crystallizes  best  from  a  solution  contain- 
ing a  small  amount  of  free  sulphuric  acid.  Calcium  hydroxide 
can  be  used  instead  of  calcium  carbonate. 

Description.  —  Colorless  prisms,  having  a  sharp  but  pleasant 
acid  taste.  Readily  soluble  in  water  and  alcohol,  and  slightly 
soluble  in  ether.  The  crystals  are  anhydrous  and  not  deliques- 
cent. 


252  ACIDS. 

VALERIANIC  ACID. 

ACIDUM  VALERIANICUM. 

(Acidum  Valericum — Valeric  Acid.) 
HC5H9O2=io2. 

This  acid  exists  in  valerian,  anthemis,  angelica,  humulus  and 
viburnum,  being  formed  by  the  oxidation  of  volatile  oils  or  other 
natural  constituents,  and  accordingly  present  in  larger  proportion 
in  old  lots  of  these  plants  which  have  been  somewhat  exposed 
to  the  air.  It  is  now  prepared  by  the  action  of  chromic  anhydride 
upon  amyl  alcohol,  as  illustrated  in  the  process  for  the  manufac- 
ture of  sodium  valerate.  See  "Sodium  Valerate." 

Valeric  acid  may  be  conveniently  prepared  by  adding  sulphric 
acid  to  a  strong  solution  of  sodium  valerate  in  water.  The  oily 
layer  rising  to  the  surface  of  the  mixture  is  valeric  acid.  This 
is  separated  from  the  watery  liquid  containing  the  sodium  sul- 
phate, then  deprived  of  water  by  repeatedly  shaking  it  with  strong 
sulphuric  acid,  and,  after  separation  from  the  sulphuric  acid,  the 
product  is  distilled. 

Description. — A  thin,  oily,  colorless  liquid,  having  a  very  char- 
acteristic, sharp,  disagreeable,  penetrating,  valerian-like  odor. 
Its  taste  is  pungent,  acid,  extremely  disagreeable.  Soluble  in 
from  26  to  30  parts  of  water.  Soluble  in  all  proportions  in  alco- 
hol and  ether.  Its  sp.  w.  is  about  0.9536  at  o°  C. 


OTHER   PREPARATIONS. 
ALUM. 

ALUMEN. 

(Potassium  Alum.     Aluminum-Potassium  Sulphate.) 
AlK(S04)2.i2H20:=474. 

Aluminum  sulphate 25  parts 

Potassium   sulphate 7  parts 

Water .' 60  parts 

Diluted  sulphuric  acid  (10%) i  part 

Heat  the  water  to  boiling.  Add  the  aluminum  sulphate.  Then 
add  the  potassium  sulphate,  stirring  well.  Add  the  diluted  sul- 
phuric acid.  Filter  if  necessary.  Set  the  solution  aside  to  cool 
and  crystallize. 

Evaporate  the  mother-liquid  to  obtain  additional  crops  of  crys- 
tals as  far  as  practicable.  Recrystallize  the  product  once  or  twice 
as  may  be  necessary. 

Notes.  The  aluminum  sulphate  used  may  be  that  obtained 
from  cryolite,  as  described  under  Aluminum  Sulphate. 

Crystallized  Alum. 

Potash  alum 2  parts 

Water   18  parts 

Diluted  sulphuric  acid I  part 

Make  a  solution  with  the  aid  of  heat.  Filter.  Crystallize  the 
salt  in  the  usual  way. 

Very  large  and  well-developed  crystals  may  be  easily  obtained 
if  the  crystallization  proceeds  slowly  by  spontaneous  evapora- 
tion and  with  the  solution  at  perfect  rest.  To  start  crystallization 
a  few  small  crystals  of  pure  potash  alum  may  be  placed  in  the 
solution.  The  crystals  should  not  be  permitted  to  rest  on  one 
side  throughout  the  process,  but  should  be  turned  over  occasion- 
ally in  order  that  they  may  be  equally  well  developed  on  all  sides. 

253 


254  ALUM. 

Turbidated  Alum. 

Potash  alum 20  parts 

Boiling  water 20  parts 

Diluted  sulphuric  acid I  part 

Dissolve,  filter,  and  cool  the  solution  rapidly,  stirring  it  con- 
stantly, to  as  low  a  temperature  above  the  freezing  point  of  water 
as  may  be  conveniently  attained.  Collect,  drain  and  dry  the  crys- 
talline salt. 

Description. — Alum  consists  of  large,  colorless,  octohedral 
crystals,  sometimes  modified  by  cubes,  or  occurs  in  crystalline 
fragments,  without  odor,  but  having  a  sweetish  and  strongly 
astringent  taste.  On  exposure  to  the  air,  the  crystals  are  liable 
to  absorb  ammonia,  and  acquire  a  whitish  coating. 

Soluble  in  9  parts  of  water  at  15°  C.,  and  in  0.3  part  of  boiling 
water;  it  is  also  freely  soluble  in  warm  glycerin,  but  is  insoluble 
in  alcohol. 

The  salt  has  an  acid  reaction  upon  litmus  paper. 

Dried  Alum. 

ALUMEN    EXSICCATUM. 

KA1(SOJ  2=258. 

Expose  ii  parts  of  crystallized  potash  alum  for  several  days 
to  a  temperature  of  about  80°  until  it  has  thoroughly  effloresced. 
Then  heat  it  in  a  porcelain  dish  gradually  up  to  200°,  being  care- 
ful not  to  permit  the  temperature  to  rise  above  205°,  and  continue 
the  heating  until  a  porous  white  mass  remains,  weighing  6  parts. 
When  cold,  powder  it  and  keep  it  in  a  well-closed  bottle. 

Notes.  Potassa  alum  contains  45.57  per  cent  of  water  of  crys- 
tallization. When  kept  heated  to  40°  C.  it  loses  about  2.7  per  cent 
of  that  water ;  at  47°  C.  it  loses  9.6  per  cent ;  at  60°  C.  it  loses  most 
of  its  water,  but  the  pieces  still  retain  to  a  great  extent  their  shape, 
and  the  product,  which  is  not  porous,  yields  a  clear  solution  with 
water.  At  80°  C.  the  salt  falls  to  powder,  but  still  retains  a  con- 
siderable amount  of  water.  Long-continued  drying  at  100°  C. 


ALUM.  255 

expels  all  the  rest  of  the  water  and  leaves  an  entirely  water  soluble 
product,  but  not  a  light  and  porous  one. 

When  first  effloresced  at  80°  C.  and  then  at  once  gradually  to 
between  200°  and  205°  C.  and  kept  at  that  temperature  until  its 
weight  is  reduced  to  that  of  the  anhydrous  product,  the  result  is 
a  light  and  porous  dried  alum. 

When  alum  is  at  once  heated  to  92°  C.  it  undergoes  aqueous 
fusion,  and  if  then  set  aside  to  cool  the  liquid  does  not  solidify 
until  after  long  standing. 

A  porous  and  light  product  is  to  be  much  preferred,  and  such 
a  product  can  not  be  obtained  if  the  alum  be  permitted  to  dis- 
solve in  its  water  of  crystallization.  When  heated  at  a  too  low 
temperature  the  alum  may  form  a  glassy  mass  which  can  not  be 
rendered  porous.  In  this  glassy  condition  the  alum  is  said  to 
retain  14  molecules  of  water  which  can  be  expelled  at  a  higher 
temperature,  but  the  product  is  then  heavy  and  non-porous. 

During  the  latter  part  of  the  process  of  heating  the  alum  it 
swells  and  foams  considerably  from  the  water  vapor  formed. 
Hence  the  dish  used  should  be  large  enough,  or  only  about  one- 
fourth  to  one-third  filled.  The  alum  should  not  be  stirred  during 
the  heating ;  if  stirred  it  will  not  yield  a  light  product. 

As  it  is  impracticable  for  the  student  to  regulate  the  tempera- 
ture so  as  to  maintain  it  at  between  200°  and  205°,  he  may  not 
succeed  in  making  a  perfect  product ;  but  he  can  verify  in  a  gen- 
eral way  the  statements  here  made  and  may  even  produce  a  better 
dried  alum  than  is  obtained  by  the  official  process  (U.S. P.,  1890), 
which  is  as  follows : 

"Place  100  grams  of  alum  [in  small  pieces]  in  a  shallow  porce- 
lain capsule  so  as  to  form  a  thin  layer,  and  heat  it  on  a  sand-bath 
until  it  liquefies.  Then  continue  the  application  of  a  moderate 
heat,  with  constant  stirring,  until  aqueous  vapor  ceases  to  be  dis- 
engaged, and  a  dry,  white,  porous  mass  is  obtained,  weighing  55 
grains.  When  cold,  reduce  the  product  to  fine  powder." 

Dried  alum  should  be  kept  in  tightly  closed  bottles.  Exposed 
to  a  moist  atmosphere  it  absorbs  water  quite  rapidly,  even  to  the 
extent  of  about  18  molecules,  or  over  50  per  cent  of  its  weight. 

Description. — Porous  white  masses,  or  a  white  granular  pow- 
der, odorless,  sweetish,  astringent.  Slowly  soluble  in  20  parts  of 
water  at  15°. 


256  ALUM. 

AMMONIA  ALUM. 

ALUMINI    ET    AMMONII    SULPHAS. 

Aluminum-Ammonium  Sulphate. 

A1H4N(S04)2.I2H20=453. 

Aluminum  sulphate 25  parts. 

Ammonia  water  ( 10%  of  H3N) 13  parts. 

Diluted  sulphuric  acid  ( 10%) 35  parts. 

Water    10  parts. 

Mix  the  diluted  acid  and  water  in  a  porcelain  dish.  Add  the 
ammonia  water  gradually,  stirring  well.  Then  add  the  aluminum 
sulphate ;  heat  to  boiling  for  a  few  minutes ;  filter.  Set  aside  to 
cool  and  crystallize. 

Additional  quantities  of  crystals  may  be  obtained  on  evapora- 
tion of  the  mother-liquors. 

Recrystallize  the  product  once  or  twice  to  purify  it. 

Notes.  The  aluminum  sulphate  required  may  be  obtained  from 
cryolite  by  the  process  described  under  Alumini  Sulphas. 

Description. — Colorless,  transparent,  octohedral  crystals ;  odor- 
less ;  taste  sweetish,  astringent 

Commercial  "alum"  is  now  "ammonia  alum,"  while  the  official 
alum  is  "potash  alum." 

For  most  of  the  purposes  for  which  alum  is  used,  the  ammonia 
alum  is  as  effective  as  the  potash  alum.  But  "dried  alum"  or 
"burnt  alum"  must  be  made  from  potash  alum,  and  when  alum 
is  prescribed  for  pharmaceutical  or  medicinal  purposes  the  official 
"alumen"  is,  of  course,  the  kind  intended. 

Ammonia  alum  is  somewhat  more  readily  soluble  in  water  than 
the  potash  alum;  but  in  other  respects  their  physical  properties 
are  alike.  On  warming  the  ammonia  alum  with  solution  of 
potassium  hydroxide  the  odor  of  ammonia  is  developed. 

ALUMINUM  ACETATE  SOLUTION. 
[After  the  German  and  Swiss  Pharmacopoeias.] 

Aluminum  sulphate 222  parts. 

Acetic  acid   (96% ) 3°°  Parts- 

Distilled  water 480  parts. 


ALUMINUM     CHLORIDE.  257 

Make  a  solution.     Add  to  this,  gradually,  a  mixture  made  of — 

Calcium  carbonate 100  parts. 

Distilled   water 140  parts. 

Let  the  mixture  stand  24  hours,  stirring  or  shaking  it  occa- 
sionally. 

Filter  the  liquid,  and  add,  through  the  filter,  enough  distilled 
water  to  make  the  whole  product  weight  1000  parts. 

Description. — A  clear  colorless  liquid  of  1.058  sp.  w.,  contain- 
ing 10  per  cent  of  anhydrous  basic  aluminum  acetate,  correspond- 
ing to  3.5 — 3.6  per  cent  dry  aluminum  oxide.  It  has  a  faint  odor 
of  acetic  acid,  a  sweetish  astringent  taste  and  an  acid  reaction. 

Used  as  a  disinfectant. 

Aluminum  Aceto-Tartrate  Solution. 

The  Swiss  and  other  pharmacopoeias  contain  the  following 
formula : 

Solution  of  aluminum  acetate 74  parts. 

Tartaric  acid 3  parts. 

Distilled  water 23  parts. 

Dissolve  the  tartaric  acid  in  the  solution  of  aluminum  acetate, 
and  add  the  water. 

Description. — A  colorless  solution  of  1.047  SP-  w-  Yields  upon 
evaporation  10  per  cent  of  aluminum  aceto-tartrate  dried  at  100° 
C.  Reaction  acid.  A  disinfectant. 


ALUMINUM  CHLORIDE. 

ALUMINI   CHLORIDUM. 
A1C18.6H2O=24I.2. 

Saturate  diluted  hydrochloric  acid  with  aluminum  hydroxide, 
prepared  as  described  under  that  head.  Acidulate  the  solution  by 
adding  some  more  of  the  acid ;  filter  and  evaporate  to  crystalliza- 
tion over  a  water  bath. 

It  decomposes  when  evaporated  to  dryness. 

Vol.   11—17 


258  ALUMINUM   HYDROXIDE. 

This  preparation  may  also  be  made  by  metathesis  from  alu- 
minum sulphate  and  barium  chloride. 

Description. — Colorless  crystals.  Soluble  in  0.25  part  of  water 
at  15°. 

Used  as  a  disinfectant  and  an  astringent. 

Aluminum  Chloride  Solution. 

LIQUOR  ALUMINI  CHLORIDI. 

Solution  of  aluminum  chloride  is  often  employed  as  a  disin- 
fectant. Pure  aluminum  chloride  is  not  necessary  for  this  pur- 
pose. A  good  product  is  obtained  as  follows : 

Calcium  chloride i  part 

Alum,  in  powder 2  parts 

Water. 

Dissolve  the  calcium  chloride  in  5  parts  of  water  and  the  alum 
in  15  parts  of  boiling  water.  Mix  the  solutions.  Filter.  Add 
enough  water  to  make  the  whole  product  weigh  20  parts. 

Notes.  The  product  contains  aluminum  chloride,  potassium 
chloride,  and  a  trace  of  calcium  sulphate. 

ALUMINUM    HYDROXIDE. 

ALUMINI    HYDROXIDUM. 

A1(OH)3=78. 

Alum,  in  powder I  part 

Sodium   carbonate I  part 

Distilled  water,  sufficient. 

Dissolve  each  salt  in  15  parts  of  distilled  water,  filter  the  so- 
lutions and  heat  to  boiling.  Then  having  poured  the  hot  solu- 
tion of  carbonate  of  sodium  into  a  capacious  vessel,  gradually  pour 
into  it  the  hot  solution  of  alum  with  constant  stirring,  and  add 
about  10  parts  of  boiling  distilled  water.  Let  the  precipitate  sub- 
side, decant  the  clear  liquid,  and  pour  upon  the  precipitate  20 
parts  of  hot  distilled  water.  Again  decant,  transfer  the  precipi- 
tate to  a  strainer,  and  wash  it  with  hot  distilled  water  until  the 


ALUMINUM   HYDROXIDE.  259 

washings  give  but  a  faint  cloudiness  with  test-solution  of  barium 
chloride.  Then  allow  it  to  drain,  dry  it  at  a  temperature  not 
exceeding  40°  C.,  and  reduce  it  to  a  uniform  powder. 

Reaction. 

3Na2C03+2AlK(S04)2+3H20 

=3Na2S04+K2S04+2Al  ( OH)  3+3CO2. 

Notes.  It  is  necessary  to  have  a  decided  excess  of  alkali  pres- 
ent throughout  the  process,  and  as  equal  parts  of  alum  and 
sodium  carbonate  leave  only  about  ten  per  cent  excess  of  the 
alkali,  and  as  this  excess  is  not  too  great,  these  proportions 
are  used.  Unless  a  sufficient  excess  of  alkali  be  present  from 
the  beginning  to  the  end  of  the  reaction,  and  the  liquid  still 
remains  alkaline  after  all  the  alum  has  been  decomposed,  the 
product  will  contain  sulphate.  This  explains  why  it  is  directed 
that  the  alum  solution  must  be  poured  into  the  alkali  solution, 
and  not  vice  versa;  it  also  accounts  for  the  injunction  to  add 
the  alum  solution  slowly  and  with  constant  stirring. 

Aluminum  hydroxide  is  a  very  light,  voluminous  precipitate, 
forming  an  almost  gelatinous  magma,  which  settles  very  slowly 
if  at  all,  and  is  therefore  difficult  to  wash.  It  will  of  course 
settle  less  readily  in  a  dense  liquid  than  in  one  less  dense.  Hence 
the  addition  of  hot  water  greatly  facilitates  the  washing  by  de- 
cantation.  But  prolonged  contact  with  boiling  water  changes 
the  constitution  of  the  hydroxide  from  A1(OH)3  to  OA1OH,  and 
the  latter  compound  is  insoluble  in  acids.  Hence,  the  liquid  in 
which  the  hydroxide  is  suspended  must  not  be  boiling,  but  only 
hot. 

The  washed  hydroxide  is  to  be  dried  without  much  heat  in 
order  to  avoid  its  becoming  hard  and  gritty. 

Aluminum  hydroxide  may  also  be  prepared  from  cryolite,  as 
described  under  the  title  of  Aluminum  Sulphate. 

It  is  chiefly  prepared  as  a  preliminary  step  in  the  preparation 
of  sulphate,  chloride,  nitrate,  acetate,  and  other  aluminum  salts. 
When  prepared  for  this  purpose  the  hydroxide,  after  having  been 
well  washed,  is  simply  drained  but  not  dried  before  dissolved  in 
the  proper  acid. 


26O  ALUMINUM    NITRATE. 

Description. — A  white,  light,  amorphous,  odorless  and  tasteless 
powder,  insoluble  in  water  and  in  alcohol. 


ALUMINUM    NITRATE    SOLUTION. 

LIQUOR   ALUMINI    NITRATIS. 

Containing  about  10  per  cent  of  A1(NO3)39H2O=375. 

Alum,  powdered 33  parts 

Sodium  carbonate 30  parts 

Nitric  acid 20  parts 

Dissolve  the  alum  and  the  sodium  carbonate  separately,  each 
in  450  parts  of  boiling  water ;  filter  the  solutions ;  pour  the  solu- 
tion of  alum  into  the  solution  of  sodium  carbonate,  stirring 
briskly.  Add  300  parts  of  boiling  water.  Digest  the  mixture  at 
a  gentle  heat  until  the  evolution  of  carbon  dioxide  ceases;  wash 
the  precipitate  with  hot  distilled  water,  first  by  decantation  and 
afterward  on  a  muslin  strainer,  until  the  washings  cease  to 
give  a  precipitate  with  test-solution  of  barium  chloride.  Let 
the  magma  drain  thoroughly,  and  then  dissolve  it  in  the  nitric 
acid.  Evaporate  the  solution  to  260  parts. 

Notes.  The  reaction  taking  place  between  the  alum  and  so- 
dium carbonate,  and  notes  on  that  part  of  the  process,  are  given 
under  the  title,  aluminum  hydroxide. 

This  solution  is  employed  as  an  astringent  and  disinfectant. 

ALUMINUM    OLEATE. 

ALUMINI   OLEAS. 

A1(C18H3302)  3=870. 

Potash  alum 60  Gm 

White  Castile  soap,  in  fine  powder no  Gm 

Dissolve  the  alum  in  3,600  ml  of  water,  and  the  soap  in  1,800 
ml  of  hot  water.  Pour  the  cold  soap  solution  gradually  into 
the  alum  solution.  Warm  the  mixture  until  the  oleate  separates. 


ALUMINUM    SULPHATE.  26l 

Decant  the  mother  liquor,  wash  the  oleate  twice  with  hot  water, 
using  3,000  ml  of  water  each  time,,  and  then  collect  the  product. 

Reaction. 

6NaC18H33O2+2KAl  ( SO4 )  2 

=2Al(C18H3302)3+K2S04+3Na2S04. 

Notes.  To  free  this  oleate  from  water  it  must  be  melted  in  an 
evaporating  dish  by  very  gentle  heat  over  the  water-bath. 

The  yield  is  about  100  Gm  or  slightly  over  that  amount. 

Description. — Aluminum  oleate  is  a  soft,  white  plaster,  contain- 
ing 5.86  per  cent  of  aluminum  oxide. 

ALUMINUM    SULPHATE. 

ALUMINI   SULPHAS. 

Al2(SO4)3.i6H2O=63o. 

Powdered  cryolite 10  parts 

Lime  in  powder 8  parts 

Sodium  bicarbonate,  about 12  parts 

Diluted  sulphuric  acid,  about 140  parts 

Water. 

Slake  the  lime  with  3  parts  of  water.  Add  40  parts  of  water 
and  mix  well.  Then  add  the  powdered  cryolite,  stirring  thor- 
oughly. Boil  for  six  or  eight  hours,  stirring  frequently,  and 
replacing  from  time  to  time  the  water  lost  by  evaporation. 
Filter  the  mixture  through  a  muslin  strainer,  and  wash  the  resi- 
due on  the  strainer  with  hot  water,  adding  the  washings  to  the 
previous  filtrate.  Boil  the  liquid,  adding  small  quantities  of  so- 
dium carbonate  until  all  the  iron  has  been  precipitated  (as  may 
be  determined  by  the  addition  of  test-solution  of  potassium  fer- 
rocyanide  to  a  test-portion  acidified  with  hydrochloric  acid). 

Then  add  a  solution  of  sodium  bicarbonate  to  the  hot  liquid  as 
long  as  precipitation  is  produced,  taking  care  not  to  add  an 
excess.  Wash  the  precipitated  aluminum  hydroxide  with  hot 
water,  until  the  washings  are  free  from  sodium  carbonate.  Dis- 
solve the  washed  aluminum  hydroxide  in  the  diluted  sulphuric 
acid,  evaporate  the  solution  to  a  density  of  about  1.20  and  set  it 


262  ALUMINUM   SULPHATE. 

aside  to  crystallize,  or  evaporate  to  a  syrupy  consistence,  and 
set  it  aside  to  solidify  on  cooling. 

Reaction. 

AlF3.3NaF+3CaO=Al ( NaO)  3+3CaFe2 ;  then 
Al(NaO)3+3NaHC03=Al(OH)3+3Na2C03;  and,  finally, 
2Al(OH)3+3H2SO4+ioH2O=Al2(SO4)8.i6H2O. 

Notes.  This  aluminum  sulphate  is  used  for  the  preparation  of 
alum  (see  alum  and  ammonia  alum). 

The  quantity  of  sodium  bicarbonate  indicated  may  not  all  be 
required. 

It  is  necessary  that  the  diluted  sulphuric  acid  should  be  com- 
pletely saturated  with  aluminum  hydroxide,  or,  in  other  words, 
that  some  of  that  hydroxide  should  remain  undissolved  in  the 
acid.  Hence  it  is  recommended  that  only  three-fourths  of  the 
diluted  acid  be  used  at  first,  and  that  after  all  of  the  aluminum 
hydroxide  shall  have  been  added,  the  remainder  of  the  sulphuric 
acid  be  added  gradually  according  to  the  indications.  The  whole 
quantity  named  can  probably  be  saturated  with  the  aluminum 
hydroxide  obtained  from  the  quantity  of  cryolite  used  unless  a 
portion  of  the  hydroxide  be  lost  in  the  process  of  washing. 
But  the  results  are  somewhat  variable  and  it  is  therefore  neces- 
sary to  proceed  cautiously. 

Pure  Aluminum  Sulphate. 
Al2(SO4)3.i6H2O=63o. 

Alum 30  parts 

Sodium   carbonate 30  parts 

Sulphuric  acid 9  parts 

Dissolve  the  alum  and  the  sodium  carbonate,  each  in  400  parts 
of  boiling  water,  filter,  and  pour  the  hot  alum  solution  into  the 
hot  solution  of  sodium  carbonate,  stirring  constantly.  Digest 
the  mixture  at  a  gentle  heat  until  the  evolution  of  carbon  dioxide 
ceases.  Wash  the  precipitate  with  hot  water  until  the  washings 
no  longer  yield  a  precipitate  with  test  solution  of  barium  chloride. 
Then  let  the  precipitated  aluminum  hydrate  drain  as  far  as  pos- 
sible, and  dissolve  it  with  the  aid  of  gentle  heat  in  the  sulphuric 


AMMONIA.  263 

acid,  previously  diluted  with  50  parts  of  water ;  filter  the  solution, 
evaporate  it  with  constant  stirring,  over  a  water  bath,  until  a 
nearly  dry  white  salt  remains. 

Notes.  Aluminic  hydroxide  is  first  prepared.  See  article 
Aluminum  Hydroxide,  p.  258,  for  reaction  and  notes.  Then  the 
sulphuric  acid  is  saturated  with  the  aluminum  hydroxide.  Care 
must  be  taken  not  to  lose  any  of  the  hydroxide  in  the  process 
of  washing  it,  for  if  the  quantity  is  insufficient  the  acid  can  not 
be  saturated  and  the  product  will  then  contain  free  sulphuric 
acid.  If  there  is  any  reason  for  believing  that  any  portion  of  the 
aluminum  hydroxide  has  been  wasted,  the  amount  of  sulphuric 
acid  used  may  be  reduced  so  as  to  insure  its  saturation. 

Description. — Pure  aluminum  sulphate  is  a  white  crystalline 
powder ;  odorless ;  taste  sweetish,  astringent.  Permanent  in  the 
air  if  properly  prepared.  Soluble  in  1.2  parts  of  water  at  15°. 
Insoluble  in  alcohol. 


AMMONIA    WATER. 

LIQUOR   AMMONII    HYDROXIDI. 

H4NOH— 35,  dissolved  in  water. 

Ammonium  chloride,  in  coarse  powder.  .     80  parts 

Lime 100  parts 

Distilled  water,  water,  each  sufficient. 

Slake  the  lime  with  2  parts  of  water;  add  the  ammonium 
chloride  to  20  parts  of  water ;  mix  the  whole  well,  and  immedi- 
ately introduce  the  mixture  into  an  iron  flask.  Connect  the  flask 
at  once,  by  means  of  corks,  glass  tubes  and  rubber  stoppers, 
with  a  Woulff  bottle  of  the  capacity  of  20  parts.  Connect  this 
with  a  second  Woulff  bottle  of  the  same  size,  and  this  in  turn 
with  a  receiver  of  the  capacity  of  160  parts,  and  containing  20 
parts  of  distilled  water.  Connect  the  receiver  with  still  another 
bottle  containing  16  parts  of  distilled  water.  The  Woulff  bot- 
tles are  to  be  empty.  The  second  Woulff  bottle  and  the  receiver 
must  each  be  provided  with  a  siphon  safety  tube  charged  with  a 
very  short  column  of  mercury. 


264  AMMONIA. 

The  iron  flask  is  placed  in  a  sand-bath,  and  heat  is  applied. 
The  receiver  is  to  be  cooled  by  cold  water.  All  joints  being 
tight,  the  heat  is  gradually  raised  and  continued  until  no  more 
gas  passes  over. 

Reaction.    2H4NCl+Ca  ( OH)  2=2H4NOH+CaCl2. 

Notes.  For  experimental  purposes  a  glass  flask  may  be  used 
instead  of  that  of  iron,  but  the  process  cannot  then  be  continued 
until  all  the  gas  has  been  obtained  which  the  ammonium  chloride 
will  yield. 

The  water  is  added  to  the  lime  and  ammonium  chloride  in 
order  to  facilitate  the  reaction.  The  calcium  hydrate  must  be 
allowed  to  become  cool  before  mixing  it  with  the  ammonium 
chloride. 

At  the  conclusion  of  the  operation  there  will  be  considerable 
quantities  of  liquid  in  all  four  bottles.  The  Woulff  bottles  will 
contain  discolored  ammonia  solutions ;  the  third  bottle  or  receiver, 
contains  a  strong  solution  of  ammonia,  which  is  to  be  diluted 
with  distilled  water  until  of  the  required  strength;  the  terminal 
bottle  contains  weaker  ammonia  solution,  which  may  be  strength- 
ened by  charging  it  with  an  additional  quantity  of  gas  obtained 
by  heating  in  a  flask  the  contents  of  the  Woulff  bottles. 

If  ammonium  carbonate  is  used  instead  of  chloride,  less  heat 
will  be  required,  but  in  that  case  the  gas  must  be  passed  through 
a  bottle  containing  milk  of  lime  to  fix  the  carbon  dioxide. 

In  order  to  prevent  accidents  which  may  cause  serious  results 
the  Pharmacopoeia  directs  that  stronger  ammonia  water  shall 
be  kept  in  strong  glass  stoppered  bottles,  only  partially  filled, 
and  put  in  a  cool  place.  If  the  containers  are  not  sufficiently 
strong,  and  are  too  nearly  full  and  kept  in  a  warm  place,  they 
may  burst.  The  gas  is  extremely  caustic  and  acrid.  To  inhale 
or  smell  ammonia  without  due  caution  is  attended  with  danger, 
and  a  full  container  with  tightly  fitting  glass-stopper  should 
never  be  opened,  especially  if  it  is  not  cool,  without  turning  the 
face  aside  from  it. 

Valuation.  Two  water-solutions  of  ammonium  hydroxide  are 
contained  in  the  Pharmacopoeia  of  the  United  States.  One  is 
called  aqua  ammoniac,  ammonia  water,  and  is  required  to  be  of  a 
strength  corresponding  to  10  per  cent  of  H3N ;  the  other  is  called 


AMMONIA.  265 

aqua  ammoniac  fortior,  stronger  water  of  ammonia,  representing 
28  per  cent  of  H3N. 

To  neutralize  3.4  Gm  (or  3.54  ml)  of  ammonia  water  requires 
20  ml  of  normal  sulphuric  acid;  to  neutralize  1.7  Gm  (or  1.88 
ml)  of  stronger  ammonia  water  requires  28  ml  of  normal  sul- 
phuric acid.  Each  ml  of  normal  sulphuric  acid  required  to 
neutralize  a  solution  of  ammonium  hydroxide  corresponds  to 
0.017  Gm  of  H3N.  The  indicator  prescribed  in  the  United  States 
Pharmacopoeia  is  rosolic  acid. 

Description. — Colorless,  transparent,  suffocatingly  pungent, 
acrid,  alkaline. 

The  ammonia  water  (10  per  cent  H3N)  has  the  sp.  w.  0.960 
at  15°  ;  the  stronger  ammonia  water  (28  per  cent  H3N)  has  the 
sp.  w.  0.901  at  the  same  temperature. 


AMMONIA    SPIRIT. 

SPIRITUS    AMMONIAE. 

An  alcoholic  solution  of  ammonia  containing  10  per  cent  of  the 
gas. 

Stronger  water  of  ammonia 500  ml 

Alcohol i  ,000  ml 

Put  the  ammonia  water  into  a  boiling-flask  of  the  capacity  of 
about  1,000  ml;  connect  this  with  a  bottle  of  1,500  ml  capacity 
to  be  used  as  a  receiver  and  containing  the  alcohol.  The  bent 
glass  tube  connecting  the  flask  and  the  receiver  should  be  of 
about  10  millimeters'  diameter.  Place  the  receiver  in  ice-cold 
water.  Fit  a  thermometer  in  the  flask. 

Now  heat  the  flask  carefully  and  gradually,  by  means  of  a 
water  bath,  up  to  about  60°  C.,  and  maintain  this  temperature 
in  the  bath  for  ten  minutes.  Then  disconnect  the  receiver  and 
test  the  solution  of  ammonia  with  normal  sulphuric  acid  to  de- 
termine its  ammoniacal  strength ;  20  ml  of  that  acid  should 
exactly  neutralize  3.4  Gm  or  4.2  ml  of  official  spirit  of  ammonia. 
Having  ascertained  the  quantity  of  normal  sulphuric  acid  re- 
quired to  neutralize  the  product,  adjust  the  strength  accordingly 
to  the  required  standard. 


266  AMMONIUM    ACETATE. 

Notes.  The  solution  obtained  is  usually  stronger  than  10  per 
cent,  in  which  case  it  simply  requires  dilution  with  the  proper 
proportion  of  alcohol.  If  the  solution  be  found  to  contain  less 
than  10  per  cent  of  H3N  the  receiver  may  be  reconnected  and 
the  process  continued.  Should  the  stronger  water  of  ammonia 
used  fail  from  any  cause  to  furnish  sufficient  H3N  to  give  the 
product  the  requisite  strength,  put  a  fresh  portion  of  ammonia 
water  in  the  flask  and  repeat  the  process. 

It  has  the  sp.  gr.  0.810,  and  the  sp.  vol.  1.235. 

Aromatic  Spirit  of  Ammonia. 

Ammonium  carbonate,  in  translucent  hard 

pieces  34  Gm 

Ammonia  water 90  ml 

Oil  of  lemon 10  ml 

Oil  of  lavender  flowers I  ml 

Oil  of  nutmeg I  ml 

Alcohol 700  ml 

Distilled  water. 

To  the  ammonia  water,  contained  in  a  flask,  add  140  ml  of 
distilled  water,  and  afterwards  the  ammonium  carbonate  reduced 
to  a  moderately  fine  powder.  Close  the  flask  and  agitate  the 
contents  until  the  carbonate  is  dissolved.  Introduce  the  alcohol 
into  a  graduated  bottle  of  suitable  capacity,  add  the  oils,  then 
gradually  add  the  solution  of  ammonium  carbonate,  and  after- 
wards enough  distilled  water  to  make  the  product  measure  one 
liter.  Set  the  liquid  aside  during  twenty-four  hours  in  a  cool 
place,  occasionally  agitating,  then  filter  it  through  paper,  in  a 
well-covered  funnel. 

Keep  the  product  in  glass-stoppered  bottles,  in  a  cool  place. 

Description. — A  nearly  colorless  liquid  when  freshly  prepared, 
but  gradually  acquiring  a  somewhat  darker  tint. 
It  has  a  pungent,  ammoniacal  odor  and  taste. 
Specific  gravity:   about  0.905  at  15°  C. 

AMMONIUM    ACETATE    SOLUTION. 

LIQUOR   AMMONII    ACETATIS. 

[Spiritus  MindererL] 
An  aqueous  solution  containing  about  7  per  cent  of  ammonium 


AMMONIUM  ACETATE.  267 

acetate    (H4NC2H3O.,=77)    together   with   small   quantities   of 
acetic  acid  and  carbonic  acid. 


Ammonium  carbonate 5  Gm 

Diluted  acetic  acid. .  100  ml 


Add  the  ammonium  carbonate  gradually  to  the  cold  diluted 
acid,  and  stir  until  it  is  dissolved. 

This  preparation  should  be  freshly  made  when  wanted. 

Reaction. 

H4NHCO8.H4NNH2CO2+3HC2H8O2 

=3H4NC2H302+H20+2C02. 

Notes.  The  ammonium  carbonate  used  must  be  in  hard 
translucent  pieces,  free  from  white  pulverulent  bicarbonate. 

To  make  a  preparation  such  as  the  Pharmacopoeia  intends, 
the  diluted  acid  should  be  cold  in  order  that  the  free  carbonic 
acid  which  is  formed  may  dissolve  in  sufficient  quantity  in  the 
liquid.  The  presence  of  this  carbonic  acid  renders  it  imprac- 
ticable to  determine  the  point  of  neutralization  by  means  of  test- 
paper;  but  the  preparation,  as  made,  is  slightly  acid.  The  solu- 
tion should  have  a  pure  acidulous  saline  taste,  or  the  saline 
taste  modified  only  by  that  of  the  carbonic  acid ;  a  slight  excess 
of  acetic  acid  is  desirable ;  but  any  excess  of  alkali  is  objectionable. 
Even  when  neutral  the  solution  gives  an  acid  reaction  to  litmus 
paper  owing  to  the  carbonic  acid. 

When  the  ammonium  carbonate  dissolves  in  the  acetic  acid  the 
temperature  is  lowered,  on  account  of  the  liberation  of  carbonic 
acid  gas.  This  fall  of  the  temperature  of  the  liquid  is  advantage- 
ous, as  it  aids  the  solution  of  another  portion  of  the  gas. 

In  some  pharmacopoeias  ammonia  water  is  used  instead  of 
ammonium  carbonate.  In  this  case  the  temperature  rises.  Test- 
paper  can  be  used  to  ascertain  the  reaction  when  this  method 
is  followed,  but  it  is  directed  that  the  solution  shall  be,  not 
neutral,  but  slightly  acid. 

The  preparation  must  not  be  filtered  as  that  would  expel  nearly 
all  the  carbonic  acid. 


268  AMMONIUM    CITRATE. 

AMMONIUM    CITRATE    SOLUTION. 

LIQUOR   AMMONII    CITRATIS. 

A  solution  of  ammonium  citrate  each  ml  of  which  contains 
0.50  Gm  of  (H4N)3C6H5O7  is  often  employed  in  clearing  cer- 
tain liquids  containing  iron  compounds  and  liable  to  become 
cloudy  or  to  form  precipitates.  Small  additions  of  such  a  solu- 
tion to  the  preparations  known  as  "beef,  wine  and  iron"  and 
elixirs  containing  phosphate  or  pyrophosphate  of  iron  associated 
with  organic  substances  prevent  the  formation -of  certain  pre- 
cipitates containing  iron,  or  dissolve  them  when  formed.  Such 
a  solution  may  also  be  advantageously  employed  in  the  prepara- 
tion of  soluble  phosphate  and  pyrophosphate  of  iron. 

It  is  prepared  as  follows : 

Citric  acid . 500  Gm 

Stronger  ammonia  water  (28%  of  H3N)  .  .   430  ml 
Distilled  water. 

Dissolve  the  acid  in  the  ammonia  water.  Neutralize  perfectly 
by  adding  as  much  ammonia  water  as  may  be  required.  Then 
add  enough  distilled  water  to  make  the  whole  measure  1,250  ml. 

Solution  of  Di-ammoniutn-Hydrogen  Citrate, 

may  be  prepared  by  adding  250  Gm  of  citric  acid  to  1,250  ml 
of  the  solution  of  normal  ammonium  citrate  just  described  and 
then  diluting  with  enough  distilled  water  to  make  the  whole 
measure  1,800  ml. 

Each  ml  of  this  solution  contains  0.50  Gm  of  di-ammonium- 
hydrogen  citrate  (H4N)2HC6H5O7. 

This  solution  is  frequently  used  in  the  preparation  of  the 
soluble  phosphate  and  pyrophosphate  of  iron. 

AMMONIUM    BENZOATE. 

AMMONII    BENZOAS. 

H4NC7H502=i39. 

Benzoic  acid 20  parts 

Distilled  water • 40  parts 

Water  of  ammonia,  sufficient. 


AMMONIUM  BICARBONATE.  269 

Dissolve  the  benzoic  acid  in  33  parts  of  water  of  ammonia 
previously  diluted  with  the  water.  Evaporate  over  a  water-bath 
by  gentle  heat,  adding  a  little  more  ammonia  water  from  time  to 
time,  if  necessary  to  keep  the  alkali  in  constant  excess,  so  as  to 
prevent  the  formation  of  acid  ammonium  benzoate,  which  is  less 
soluble.  When  reduced  to  50  parts  set  aside  to  crystallize.  Col- 
lect and  dry  the  crystals.  The  mother  liquor  will  yield  more 
crystals  after  evaporation,  keeping  the  ammonia  slightly  in  ex- 
cess as  before. 

Reaction.     HC7H5O2+H4NOH=H4NC7H5O2+H2O. 

Description. — White,  thin,  lamellar  crystals,  odorless  or  having 
a  faint  odor  of  benzoic  acid;  soluble  in  5  or  6  parts  of  cold 
water,  1.2  parts  of  boiling  water,  30  parts  of  alcohol,  7.6  parts 
boiling  alcohol,  or  8  parts  of  glycerin. 

Should  be  kept  in  tightly  closed  bottles. 

AMMONIUM    BICARBONATE. 

AMMONII   BICARBONAS.      . 

H4NHC03= 79. 

Stronger  ammonia  water  (28%  of  H3N),  any  desired  quantity. 

Carbon  dioxide. 

Conduct  a  stream  of  carbon  dioxide  into  the  stronger  am- 
monia water  contained  in  a  flask  keeping  the  flask  and  contents 
cool  with  running  water.  Continue  the  current  of  CO2  until  the 
gas  is  no  longer  absorbed.  The  salt  crystallizes  from  the  solu- 
tion. Separate  the  crystals  by  turning  the  contents  of  the  flask 
into  a  funnel  provided  with  a  strainer  or  perforated  diaphragm; 
drain  well,  and  dry  them  over  sulphuric  acid. 

Keep  the  product  in  a  tightly  closed  bottle  in  a  cool  place. 

Reaction.     H4NOH+CO2=H4NHCO3. 

Notes.  Erdmann  recommends  putting  the  concentrated  am- 
monia water  in  a  small  flask  closed  by  a  stopper  bearing  a  short 
glass  tube  extending  down  nearly  to  the  surface  of  the  liquid 
but  not  dipping  into  it.  The  carbon  dioxide  is  to  be  conducted 
into  the  flask  through  that  tube.  Normal  ammonium  carbonate 


27O  AMMONIUM    BROMIDE. 

is  first  precipitated  but  redissolves.  After  the  liquid  has  stood 
for  some  time  under  the  pressure  of  the  gas,  the  bicarbonate  is 
separated.  When  no  more  crystals  are  formed  a  stratum  of 
alcohol  cautiously  laid  over  the  mother  liquor  will  cause  the 
deposition  of  an  additional  crop.  The  salt  may  best  be  preserved 
in  glass  tubes  filled  with  carbon  dioxide  and  sealed. 

Another  Method. 

Dissolve  ouc  the  ammonium  carbonate  from  powdered  ordi- 
nary ammonium  carbonate  by  macerating  it  with  twice  its  weight 
of  alcohol  for  a  few  minutes.  After  separating  the  alcoholic 
solution  of  the  carbonate,  wash  the  undissolved  ammonium  bi- 
carbonate with  another  portion  of  alcohol,  using  the  same  quan- 
tity as  before.  Expose  the  product  to  the  air  until  the  alcohol 
has  evaporated,  and  then  bottle  it. 

The  carbonate  may  also  be  removed  by  macerating  the  ordi- 
nary ammonium  carbonate  for  two  hours  with  twice  its  weight 
of  water. 

Description. — Colorless  crystals,  or  a  white  crystalline  powder 
of  ammoniacal  taste  and  faintly  ammoniacal  odor  (or  nearly 
odorless  if  quite  dry).  Soluble  in  5.5  parts  of  water  at  15°. 
Insoluble  in  alcohol. 

AMMONIUM    BROMIDE. 

AMMONII    BROMIDUM. 

H4NBr=98. 

Iron  wire 4  parts 

Bromine 12  parts 

Ammonia  water 25  parts 

Distilled  water. 

Put  the  iron  wire  into  a  flask,  add  50  parts  of  warm  (not 
hot)  water,  and  then  gradually  add  9  parts  of  bromine.  Put  a 
loose  plug  of  cotton  into  the  neck  of  the  flask,  and  shake  gently 
from  time  to  time  until  a  greenish  liquid  is  obtained  having  no 
odor  of  bromine.  Filter  this  solution  of  ferrous  bromide,  add 
the  remainder  of  the  bromine  to  the  filtrate  and  shake  gently 
so  that  a  uniform  solution  may  be  obtained. 


AMMONIUM    BROMIDE.  271 

Pour  this  solution  into  the  ammonia  water  previously  diluted 
with  50  parts  of  distilled  water.  Shake  well.  Heat  the  mix- 
ture over  the  water-bath  for  half  an  hour.  Then  filter.  When 
the  liquid  has  passed  through  the  filter,  wash  the  residue  upon 'it 
with  some  hot  distilled  water,  letting  the  washings  run  into  the 
filtered  solution. 

Evaporate  the  liquid  in  a  porcelain  dish  until  a  pellicle  begins 
to  be  formed.  Then  stir  the  contents  with  a  glass  rod  while 
continuing  the  evaporation  until  a  granular  salt  remains.  Should 
this  not  be  perfectly  white  or  colorless,  redissolve  it  in  its  own 
weight  of  boiling  distilled  water,  add  a  sufficient  quantity  of  am- 
monia water  to  render  the  solution  slightly  alkaline  to  test-paper, 
boil  the  liquid  a  few  minutes,  filter  it,  and  evaporate  the  filtrate 
to  dryness  as  before. 

Reaction. 

2Fe+2Br2=2FeBr2 ;   then  3FeBr,-f  Br2=FeBr2.2FeBr3 ;   then 
FeBr2.2FeBr3+8H4NOH=8H4NBr+FeO.Fe2O3+4H2O. 

Description. — Colorless,  transparent  crystals,  or  a  white  crys- 
talline granular  salt,  odorless,  of  pungent  saline  taste.  Soluble 
in  1.50  parts  of  water,  and  in  30  parts  of  alcohol  at  15°  C. ; 
in  0.7  parts  of  boiling  water,  and  in  15  parts  of  boiling  alcohol. 

Another  Method. 

Bromine 25  parts 

Ammonia  water. 

Water. 

Hydrogen  sulphide. 

Shake  200  parts  of  water  with  5  parts  of  bromine.  Conduct 
a  stream  of  hydrogen  sulphide  into  the  liquid.  When  the  liquid 
is  no  longer  rendered  turbid  by  the  hydrogen  sulphide,  add  an- 
other 5  parts  of  bromine,  and  again  direct  hydrogen  sulphide 
into  the  liquid  until  the  red  color  disappears.  Repeat  the  addi- 
tion of  bromine,  5  parts  at  a  time,  and  the  treatment  with  hy- 
drogen sulphide  until  all  of  the  bromine  has  been  used  and  con- 
verted into  hydrobromic  acid  by  the  current  of  hydrogen  sul- 
phide. 

Filter  out  the  sulphur  and  heat  the  filtrate  to  expel  the  excess 


AMMONIUM    CARBONATE. 

of  hydrogen  sulphide  from  the  liquid.  When  filter  paper  moist- 
ened with  a  solution  of  lead  acetate  is  no  longer  blackened  by 
the  liquid,  filter  again.  Supersaturate  the  filtrate  with  am- 
monia (about  60  parts  will  be  required). 

Evaporate  the  solution  of  ammonium  bromide  until  salt  be- 
gins to  separate.  Then  add  a  little  more  ammonia,  after  which 
continue  the  evaporation  to  dryness,  stirring  constantly. 

Reaction. 

Br2+H2S=2HBr+S;  then 
HBr+H4NOH=H4NBr+H2O. 


AMMONIUM    CARBAMATE. 

AMMONII    CAR13AMAS. 

H4N(H2NCO2)=;8. 

Dissolve  the  ammonium  carbamate  from  powdered  ordinary 
ammonium  carbonate  with  strong  alcohol  and  evaporate  the  al- 
coholic solution  to  dryness  by  the  aid  of  very  moderate  heat  (not 
exceeding  25°). 

Description. — A  white  powder  readily  soluble  in  water  and  in 
alcohol. 

AMMONIUM    CARBONATE— OFFICINAL. 

AMMONII    CARBON  AS   OFFICINALIS. 

(Hartshorn  Salt.) 
Approximately  H4NHCO3.H4NH2NCO2=i57. 

This  is  a  somewhat  variable  mixture  of  ammonium-hydrogen 
carbonate  and  ammonium  carbamate. 

It  is  manufactured  on  a  large  scale  by  heating  a  mixture  of  am- 
monium sulphate  (or  ammonium  chloride)  and  calcium  carbonate, 
when  the  so-called  ammonium  carbonate  sublimes  and  is  con- 
densed. 


AMMONIUM    CARBONATE.  273 

Description. — Hard,  colorless  or  white,  translucent  (nearly 
transparent  in  thinner  fragments),  having,  when  quite  hard  and 
not  effloresced,  but  a  faint  ammoniacal  odor  if  not  confined  in  a 
closed  vessel.  When  exposed  to  the  air  it  becomes  covered  with 
a  white  efflorescence,  and  finally  converted  into  porous  lumps 
or  white  powder.  Confined  in  a  closed  vessel  the  salt  causes  the 
vessel  to  be  filled  with  vapor  of  a  strongly  ammoniacal  odor. 
The  taste  is  sharp  and  saline. 

It  is  slowly  but  completely  soluble  in  from  4  to  5  parts  of 
water  at  15°.  Hot  water  decomposes  it. 

Alcohol  dissolves' out  the  carbamate,  leaving  the  acid  ammonium 
carbonate  as  a  pulverulent  residue. 

The  reaction  of  ammonium  carbonate  is  strongly  alkaline. 

Only  hard,  translucent  pieces  of  ammonium  carbonate  should 
be  used  for  pharmaceutical  purposes.  Pieces  covered  with  a 
white  coating  may  be  scraped,  and  the  hard  translucent  interior 
used.  When  porous  and  white  throughout,  the  salt  should  be 
used  only  in  the  production  of  ammonium  salts  in  cases  where 
the  result  is  not  affected  by  the  condition  of  the  ammonium  car- 
bonate. 

This  substance  must  be  kept  in  tightly  closed  bottles  in  a  cool 
place. 

AMMONIUM    CARBONATE— TRUE. 

AMMONII    CARBONAS    VERUS. 

(Normal  or  Neutral  Ammonium  Carbonate.) 
(H4N)2C03.H20=u4. 

Ordinary  ammonium  carbonate 157  parts 

Stronger  ammonia  water 63  parts 

Distilled  water 8  parts 

Digest  them  together  for  two  days  in  a  closed  wide-mouthed 
bottle  at  from  20°  to  25°.  The  whole  contents  form  a  solid 
crystalline  mass,  which  constitutes  the  di-ammonium  carbonate. 

Keep  the  product  in  a  tightly  closed  bottle  in  a  cool  place. 

Another  Method. 
Dissolve  eight  parts  of  the  ordinary  ammonium  carbonate  in 

Vol.    11—18 


274  AMMONIUM    CHLORIDE. 

nine  parts  of  warm  ammonia  water  (containing  10  per  cent  of 
H3N)  in  a  closed  bottle.  Cool  the  solution  so  that  crystals  may 
be  formed.  Collect  and  drain  the  crystals  quickly  and  press 
them  gently  between  cloths  or  bibulous  paper.  Bottle  at  once. 

Reaction. 

H4NHCO3.H4NH2NCO2+H4NOH= 2  ( H4N )  2CO3. 

Description. — Colorless  crystals  of  ammoniacal  odor  and  taste ; 
soluble  in  their  own  weight  of  water  at  15°. 

AMMONIUM    CHLORIDE— PURIFIED. 

AMMONII    CHLORIDUM    PURIFICATUM. 

H4NC1=53.4. 

The  impurities  liable  to  be  present  in  crude  "sal  ammoniac"  or 
crude,  commercial  ammonium  chloride  are  the  chlorides  and  sul- 
phates of  iron  and  of  calcium.  The  iron  compounds  may  be 
both  ferrous  and  ferric,  but  are  usually  ferrous.  Of  the  im- 
purities mentioned  the  most  common  is  ferrous  chloride.  This 
does  not  discolor  the  ammonium  chloride  until  the  sal  ammoniac 
is  exposed  to  the  air  so  that  the  ferrous  salt  is  oxidized  to  ferric. 

The  sal  ammoniac  should  be  tested  for  ferrous  salt,  ferric  salt, 
sulphates  and  calcium,  with  test  solutions  of  potassium  ferri- 
cyanide,  potassium  ferrocyanide,  barium  chloride,  and  am- 
monium carbonate  or  oxalate,  successively,  in  the  usual  way. 
Should  all  of  the  impurities  named  be  present,  they  may  be  re- 
moved as  follows : 

Dissolve  the  impure  ammonium  chloride  in  about  twice  its 
weight  of  water,  or  less.  Heat  the  solution  to  boiling.  Filter. 
Add  solution  of  barium  chloride  in  small  quantities  to  the  hot 
filtrate  and  stir  well.  As  soon  as  a  further  addition  of  barium 
chloride  no  longer  causes  turbidity  in  a  filtered  test-portion  of  the 
liquid,  add  a  solution  of  ammonium  carbonate  or  oxalate  to  com- 
pletely precipitate  the  calcium  and  the  excess  of  barium.  Filter. 
Then  add  to  the  filtrate  about  25  ml  of  strong  chlorine  water  for 
each  kilogram  of  ammonium  chloride  in  solution.  Boil  for 
twenty  or  thirty  minutes.  Then  add  enough  ammonia  water  to 


AMMONIUM    CHLORIDE.  275 

render  the  liquid  alkaline  and  to  impart  an  ammoniacal  odor  to  it. 
Filter  again.  Evaporate  the  filtrate  to  i.io  sp.  w.  and  then 
set  it  aside  to  crystallize,  or  evaporate  nearly  to  dryness  and  dry 
the  granulated  salt  perfectly  in  the  usual  way. 

When  salts  of  organic  bases  are  present  in  the  crude  sal  am- 
moniac made  from  gas  liquor  they  should  be  destroyed  by  boiling 
100  parts  of  the  crude  product  with  125  parts  of  water  and  15 
parts  of  concentrated  nitric  acid  until  no  more  acid  vapors  are 
evolved.  The  residue  may  then  be  treated  as  before  described 
to  remove  the  chlorides  and  sulphates  of  calcium  and  iron. 

Should  ferrous  chloride  be  found  to  be  the  only  impurity  pres- 
ent, treat  the  solution  of  the  impure  ammonium  chloride  with 
chlorine  water  and  ammonia  as  described.  Should  the  product 
be  not  entirely  free  from  iron  after  one  treatment,  repeat  the 
addition  of  chlorine  water,  boil  again,  add  ammonia  in  excess  as 
before  and  again  granulate  or  crystallize  the  product. 

When  ferric  chloride  is  the  only  impurity  the  process  of  purifi- 
cation is  simple : 

Crude  ammonium  chloride 20  parts 

Water 30  parts 

Ammonia  water  ( 10% ) i  part 

Dissolve  the  ammonium  chloride  in  the  water  heated  to  boiling. 
Add  the  ammonia  water.  Continue  the  boiling  for  a  few  minutes. 
Filter.  Evaporate  to  granulation.  Dry  the  product  thoroughly. 

Pure  Ammonium  Chloride 

may  be  readily  made  from  pure  diluted  hydrochloric  acid  and  pure 
ammonia  water: 

Diluted  hydrochloric  acid  (10%  of  HC1) 2  parts 

Ammonia  water  (10%  of  H3N) I  part 

Add  the  ammonia  water  gradually  to  the  acid,  stirring  well. 
Evaporate  to  granulation  or  crystallization,  and  dry  the  product. 

Reaction.     H3N+HC1=H4NC1. 

Description. — Pure  ammonium  chloride  is  a  colorless  crystalline, 
or  a  white,  granular  salt ;  odorless,  taste  saline,  cooling.  Soluble 


276  AMMONIUM  IODIDE. 

in  3  parts  of  water  of  15°,  and  in  its  own  weight  of  boiling  water. 
Nearly  insoluble  in  alcohol.  Reaction  neutral.  Volatilises  with- 
out residue  when  strongly  heated. 


AMMONIUM  IODIDE. 

AMMONII    IODIDUM. 

H4NI=  144.50. 

Potassium  iodide   6  parts 

Ammonium  sulphate   4  parts. 

Alcohol 2  parts 

Distilled  water   12  parts 

Dissolve  the  salts,  each  in  6  parts  of  distilled  water ;  filter  the 
solutions;  mix  them;  evaporate  the  filtrate  to  about  15  parts; 
set  the  liquid  aside  in  a  cool  place  for  about  twelve  hours;  add 
the  alcohol  to  the  solution  and  set  the  mixture  in  an  ice-water 
bath  until  cooled  down  to  5°  ;  separate  and  reject  the  crystals  of 
potassium  sulphate,  which  are  now  separated,  and  add  a  little 
ammonia  to  the  clear  solution  and  evaporate  it  to  dryness. 

Put  the  product  in  a  dry  bottle,  which  must  be  tightly  closed, 
and  kept  in  a  dark  place. 

Reaction.     2KI+(H4N)2SO4= 2H4NI+K2SO4. 

Notes.  The  alcohol  is  added  to  facilitate  the  separation  of  the 
potassium  sulphate,  which  is  insoluble  in  diluted  alcohol,  while 
the  ammonium  iodide  is  soluble.  The  solution  may,  after  standing 
twelve  hours,  be  cooled  to  5°  on  an  ice-water  bath  before  the  alco- 
hol is  added,  the  clear  solution  then  separated  from  the  crystals 
of  potassium  sulphate  by  throwing  the  whole  into  a  cooled  glass 
funnel  having  a  loose  plug  of  moist  cotton  placed  in  its  throat. 
The  filtrate  may  then  be  evaporated  to  dryness,  and  the  ammon- 
ium iodide  extracted  from  the  dry  salt-mass  by  means  of  warm 
alcohol,  which  will  leave  the  potassium  sulphate  undissolved.  The 
alcoholic  solution  of  ammonium  iodide  may  then  be  allowed  to 
evaporate  until  the  dry  salt  is  obtained.  The  yield  of  ammonium 
iodide  from  6  parts  of  potassium  iodide  should  be  about  5.33  parts, 
which  is  soluble  in  50  parts  of  warm  alcohol. 


AMMONIUM    NITRATE.  277 

Description. — A  white  crystalline  powder,  without  odor,  and 
having  a  sharp  saline  taste.  Very  hygroscopic.  Soluble  at  15° 
in  two-thirds  of  its  own  weight  of  water  and  in  9  parts  of  alcohol ; 
in  half  its  weight  of  boiling  water  and  in  3.7  parts  of  boiling 
alcohol. 

The  salt  is  very  unstable,  soon  turning  yellow  or  even  brown, 
and  acquiring  an  odor  of  iodine.  The  free  iodine  by  which  the 
product  is  discolored  may  be  removed  by  washing  the  salt  with 
ether  and  then  rapidly  drying  the  white  salt;  or  a  concentrated 
aqueous  solution  may  be  made  of  the  salt  and  enough  ammonium 
sulphide  solution  added  to  render  the  liquid  colorless,  after  which 
it  is  filtered  and  evaporated  to  dryness. 

AMMONIUM  NITRATE. 

AMMONII    NITRAS. 

H4NNO3=8o. 

Nitric  acid    (68% ) 10  volumes 

Ammonia  water  (10%  H3N) 7  volumes 

Distilled  water. 

Dilute  the  nitric  acid  with  10  volumes  of  distilled  water.  Place 
the  ammonia  water  in  a  large  porcelain  dish,  and  add  to  it,  gradu- 
ally, the  diluted  nitric  acid,  stirring  well.  When  all  of  the  acid 
has  been  added,  test  the  reaction  of  the  liquid  on  litmus  paper. 
If  not  distinctly  (though  faintly)  alkaline,  make  it  so  by  the 
addition  of  sufficient  ammonia  water.  Filter  the  solution  if  not 
perfectly  clear.  Evaporate  the  filtrate  until  it  acquires  the  den- 
sity of  1.25  while  still  hot.  Then  set  it  aside  to  cool  that  crystals 
may  be  formed.  Collect  and  dry  the  crystals. 

Additional  crops  of  crystals  may  be  obtained  from  the  mother 
liquor  by  further  evaporation. 

Keep  the  product  in  dry,  well  closed  bottles. 

Reaction.     H4NOH+HNO8=H4NNO8+H2O. 

Notes.  If  fused  ammonium  nitrate  is  desired  instead  of  crys- 
tals, the  salt  should  be  fused  at  a  temperature  not  exceeding 
166°  C.  and  should  be  kept  at  that  temperature  until  it  ceases 
to  give  off  watery  vapor. 

During  the  evaporation  of  a  solution  of  ammonium  nitrate  it 


278  AMMONIUM  OXALATE. 

happens  that  the  liquid  gradually  acquires  an  acid  reaction ;  this 
should  be  corrected  by  the  addition  of  enough  ammonia  to  restore 
a  slightly  alkaline  reaction  before  the  liquid  is  set  aside  to  crys- 
tallize. 

Description. — Long,  colorless,  prismatic  crystals,  or  a  fused 
white  mass.  Odorless.  Taste  sharp  and  bitter.  Hygroscopic. 
Soluble  at  15°  in  half  its  weight  of  water  or  in  20  parts  of  alcohol ; 
very  soluble  in  boiling  water,  and  in  3  parts  of  boiling  alcohol. 


AMMONIUM  OXALATE. 

AMMONII     OXALAS. 

(H4N)2C2O4.H2O=i42. 

Oxalic   acid 100  Gm 

Boiling  distilled  water 800  ml 

Ammonium  carbonate,  sufficient. 

Dissolve  the  acid  in  the  water,  neutralize  with  ammonium  car- 
bonate, raising  the  temperature,  at  the  end  of  the  neutralization, 
to  the  boiling  point ;  filter  while  hot,  and  set  aside  to  cool  and 
crystallize. 

Reaction.     2(H4NHCO3.H4NH2NCO2)+3H2C2O4 

=3(H4N)2C204+2H20+4C02. 

Notes.  About  83  Gm  of  ammonium  carbonate  will  be  required 
to  saturate  100  Gm  of  oxalic  acid.  Instead  of  83  Gm  of  ammon- 
ium carbonate,  the  corresponding  quantity  (270  ml)  of  ammonia 
water  (10  per  cent)  may  be  used.  The  solution  should  be  ren- 
dered exactly  neutral  to  test-paper,  filtered  while  hot,  and  set 
aside  to  cool  slowly.  When  the  solution  is  dilute  and  the  cooling 
and  crystallization  slow,  very  handsome  needle-shaped  crystals 
may  be  obtained.  By  evaporating  the  mother  liquor  and  again 
crystallizing,  additional  crops  of  the  salt  are  recovered. 

Description. — This  salt  crystallizes  in  rhombic  prisms,  easily 
soluble  in  water. 


AMMONIUM   PHOSPHATE.  279 

AMMONIUM  PHOSPHATE. 

AMMONII    PHOSPHAS. 

(H4N)2HP04=I32. 

Prepared  by  adding  strong  ammonia  solution  to  diluted  phos- 
phoric acid  until  a  slightly  alkaline  reaction  on  test-paper  is  pro- 
duced. The  solution  is  then  evaporated,  the  alkaline  reaction 
being  maintained  by  adding  a  little  more  ammonia  from  time  to 
time,  as  required.  The  crystals  formed  upon  allowing  the  solu- 
tion to  cool  are  collected  and  quickly  dried  on  bibulous  paper 
placed  upon  a  porous  tile. 

Ammonium  phosphate  must  be  kept  in  well-stoppered  bottles. 

Description. — Transparent,  colorless  prisms,  inodorous,  of  a 
somewhat  alkaline  saline  taste.  Readily  soluble  in  water ;  insoluble 
in  alcohol. 

AMMONIUM  SULPHATE. 

AMMONII     SULPHAS. 

(H4N)2S04=i32. 

Ammonia  water    . 2  volumes 

Diluted  sulphuric  acid 5  volumes 

Add  the  acid  gradually  to  the  ammonia  water,  stirring  the 
liquid.  Should  the  solution  not  be  alkaline  in  its  reaction  on  test- 
paper,  add  enough  additional  ammonia  water  to  render  it  alkaline. 
Filter.  Evaporate  to  crystallization.  During  the  evaporation  test 
the  liquid  from  time  to  time  with  litmus  paper,  and  add  more 
ammonia  if  necessary  to  prevent  the  solution  from  acquiring  an 
acid  reaction,  or  to  render  it  alkaline  again  should  it  become  acid 
by  the  loss  of  ammonia. 

Reaction.     2H4NOH+H2SO4=(H4N)2SO4+H2O. 

Description. — Colorless  and  odorless  crystals,  soluble  in  1.33 
parts  of  water  at  15°. 


28<D  AMMONIUM  VALERATE. 

AMMONIUM  VALERATE. 

AMMONII     VALERIANAS. 

NH4C5H9O2=ii9. 

Prepared  by  saturating  valeric  acid  with  dry  ammonia  gas, 
usually  generated  from  a  mixture  of  equal  parts  of  ammonium 
chloride  and  lime.  The  heat  produced  by  the  chemical  union  keeps 
the  salt  in  a  liquid  condition,  and  on  cooling  the  valerate  crystal- 
lizes. The  salt  cannot  be  crystallized  from  an  aqueous  solution. 

A  solution  of  ammonium  valerate  may  be  readily  prepared  by 
dissolving  102  Gm  of  valeric  acid  in  61  Gm  of  stronger  water  of 
ammonia;  if  diluted  with  distilled  water  until  it  measures  238 
milliliters,  each  ml  of  this  solution  will  contain  0.50  Gm  of  the 
salt. 

Neutral  ammonium  valerate  easily  parts  with  ammonia  and  be- 
comes acid ;  in  solution  it  is  to  be  carefully  neutralized  with  am- 
monia water. 

Description. — Colorless  crystalline  plates,  soluble  in  water  and 
alcohol,  and  having  the  odor  of  the  acid.  They  should  volatilize 
completely. 

ANTIMONY   CHLORIDE. 

ANTIMONI     CHLORIDUM. 

SbCl3=226.5. 

Antimonous  oxide 3  parts 

Hydrochloric  acid  (32%  of  HC1) 8  parts 

Heat  gently  together  in  a  porcelain  dish,  stirring  well,  until  the 
acid  ceases  to  dissolve  any  more  of  the  oxide.  Then  raise  the 
temperature  slowly  to  the  boiling  point  and  continue  boiling  until 
a  drop  of  the  liquid  deposits  crystals  on  cooling.  Then  pour  the 
liquid  into  a  retort  provided  with  a  thermometer  in  the  tubulure 
and  distill,  heating  the  retort  in  a  sand  bath.  The  distillate  at 
first  consists  of  hydrochloric  acid,  which  is  to  be  collected  separ- 
ately. As  soon  as  the  boiling  point  rises  to  200°  and  a  drop  of  the 
distillate  solidifies  on  a  cold  surface,  change  the  receiver  and  con- 


ANTIMONY    CHLORIDE.  28l 

tinue  the  distillation.    The  distillate  now  passing  over  is  antimony 
trichloride. 

Reaction.     Sb2O3+6HCl=:2SbCl3+3H2O. 

Description. — A  white  or  yellowish-white  soft  solid  or  semi- 
solid.  Very  deliquescent.  Decomposes  when  brought  in  contact 
with  water.  Soluble  in  alcohol  without  decomposition.  It  can 
be  dissolved  in  water  containing  hydrochloric  acid,  citric  acid,  or 
tartaric  acid.  It  is  also  soluble  in  glycerin. 

Antimony  Chloride  Solution. 

LIQUOR  ANTIMONI  CHLORIDI. 

A  solution  of  SbCl3  in  water  containing  hydrochloric  acid. 

Purified  antimonous  sulphide,  in  extremely 

fine  powder   100  Gm 

Hydrochloric  acid  (35%  of  HC1) 530  Gm 

Put  the  acid  in  a  flask  of  one  cubic-decimeter's  capacity.  Heat 
it  to  about  50°.  Add  the  antimonous  sulphide,  in  very  fine  powder, 
gradually  to  avoid  too  copious  evolution  of  hydrogen  sulphide. 
Shake  well.  Apply  heat,  first  gently,  then  gradually  raising  the 
temperature  to  the  boiling  point  of  the  liquid.  Boil  for  half  an 
hour.  Let  the  liquid  cool  somewhat.  Filter  it  through  muslin, 
returning  the  portion  which  first  passes  until  the  filtrate  runs 
clear.  Evaporate  the  filtrate  to  250  ml,  and  put  it  in  a  glass- 
stoppered  bottle. 

Reaction.     Sb2S3+6HCl= 2SbCl3+3H2S. 

Notes.     Read  the  notes  under  the  title  Antimony  Oxide. 

Should  the  antimony  sulphide  be  adulterated  and  leave  an  un- 
dissolved  residue  the  solution  must  be  correspondingly  deficient 
in  strength. 

The  proportions  of  antimony  sulphide  and  hydrochloric  acid 
are  those  prescribed  in  the  British  Pharmacopoeia  of  1885.  The 
quantity  of  acid  is  more  than  twice  the  quantity  required  by  theory. 
An  excess  is  necessary  to  hold  the  antimony  chloride  in  solution, 
and  a  strong  acid  is  necessary  to  act  on  the  sulphide. 


282  ANTIMONY  OXIDE. 

Description, — A  yellowish-red  liquid  of  the  odor  of  hydrochloric 
acid.  It  gives  a  white  precipitate  when  mixed  with  water.  Sp.  w. 
about  1.47;  sp.  vol.  0.680.  It  can  be  diluted  with  1.25  times  its 
own  weight  of  water  without  permanent  precipitation. 


ANTIMONY   OXIDE. 

ANTIMONI    OXIDUM. 

Sb203=28;  (or  Sb406 

Purified  antimonous  sulphide,  in  very  fine  powder.  .  100  parts 

Hydrochloric  acid  (35%  of  HC1) 530  parts 

Ammonia  water  ( 10%  of  H3N ) 115  parts 

Water. 

Put  the  hydrochloric  acid  in  a  flask  capable  of  holding  1000 
parts  of  water.  Heat  to  about  50°.  Add  the  finely  powdered  an- 
timony sulphide,  in  small  portions,  shaking  well,  and  waiting  after 
each  addition  until  the  evolution  of  hydrogen  sulphide  has  nearly 
ceased  before  adding  another  portion  of  the  sulphide  of  antimony. 
Continue  the  heat  at  50°  and  add  hot  water  from  time  to  time  to 
maintain  the  volume  of  liquid  in  the  flask,  or  to  keep  the  flask 
about  half  filled.  When  all  of  the  antimony  sulphide  has  been 
added  and  the  evolution  of  hydrogen  sulphide  becomes  very  slow, 
heat  the  contents  of  the  flask  to  boiling  and  continue  the  boiling 
for  half  an  hour,  still  adding  enough  hot  water  from  time  to  time 
to  keep  the  volume  of  the  contents  of  the  flask  nearly  constant. 
Then  let  the  liquid  cool.  Filter  it  through  muslin  into  a  porcelain 
dish.  Add  just  enough  water  to  produce  a  slight  but  permanent 
turbidity.  Boil  the  liquid  again  for  about  five  minutes.  Filter 
again.  Pour  the  filtrate  slowly  into  2500  parts  of  water  contained 
in  a  glass  or  stoneware  vessel,  stirring  the  mixture  diligently  dur- 
ing the  addition  of  the  antimony  solution  to  the  water.  Let  the 
precipitate  subside.  Siphon  off  the  supernatant  liquid  and  add 
to  the  precipitate  2500  parts  of  hot  water,  stir  well,  let  stand  until 
the  precipitate  has  settled,  and  then  draw  off  the  wash  water. 
Repeat  this  washing  once  more,  in  the  same  manner,  with  another 
2500  parts  of  hot  water,  and  siphon  off  the  liquid.  Then  add 
the  ammonia  water  to  the  precipitate,  let  the  mixture  stand  for  an 
hour,  stirring  frequently*  Collect  the  precipitate  on  a  filter  and 


ANTIMONY   OXIDE,  283 

wash  it  with  boiling  water  until  a  test-portion  of  the  washings, 
after  acidulation  with  nitric  acid,  no  longer  produces  a  cloudiness 
with  test-solution  of  silver  nitrate.  Then  drain  the  oxide  and  dry 
it  at  a  temperature  not  exceeding  100°. 

Reactions.     Sb2S3+6HCl=2SbCl3+3H2S ; 
then     4SbCl8+5H2O=2SbOCl.Sb2O8+ioHCl;     and,     finally, 
2SbOCl.Sb2O3+2H4NOH=2Sb2O3+2H4NCl+H2O. 

Notes.  A  very  large  excess  of  hydrochloric  acid  is  used  in 
order  to  hold  the  antimony  chloride  in  soltion.  Nevertheless,  the 
action  of  the  acid  upon  the  antimony  sulphide  is  slow.  A  high 
temperature  is  necessary.  The  operation  should  be  carried  out 
under  a  hood  with  a  good  draught  to  carry  off  the  vapors  of  hy- 
drogen sulphide. 

Some  hydrochloric  acid  is  lost  by  volatilization  during  the 
process  of  heating  it  with  the  antimony  sulphide.  A  hydrochloric 
acid  of  less  than  35.  per  cent  (1.17  sp.  w.)  strength  does  not  dis- 
solve the  antimony  sulphide  completely. 

The  antimonous  sulphide  should  be  pure,  and  in  very  fine  ("im- 
palpable") powder.  It  may  be  tested  before  being  used,  to  see 
that  it  is  soluble  in  the  strong  hydrochloric  acid  without  any  resi- 
due. 

The  purified  antimonous  sulphide  of  the  Pharmacopoeia,  al- 
though nearly  or  quite  free  from  arsenic,  may  contain  some  lead. 
The  lead  chloride  derived  from  an  impure  antimony  sulphide  is 
washed  out  from  the  precipitated  "oxychloride  of  antimony"  by 
means  of  hot  water. 

Sodium  carbonate  may  be  used  instead  of  ammonia  water  (us- 
ing 95  parts  of  the  carbonate  in  place  of  115  parts  of  ammonia 
water). 

Description. — A  heavy,  light-grayish,  or  nearly  white,  odorless 
and  tasteless  powder,  insoluble -in  water  and  in  alcohol.  It  turns 
yellow  when  heated,  but  becomes  white  again  on  cooling. 

Another   Method. 
Heat  powdered  antimonous  sulphide  in  the  air  until  sulphurous 


284  ANTIMONY   OXYCHLORIDE. 

vapors  cease  to  be  given  off  and  a  fused,  glassy  residue  is  ob- 
tained : 

2Sb2S3+9O2=2Sb2O3+6SO2. 

The  glassy  antimonous  oxide  is  translucent  and  may  be  reduced 
to  a  white  powder. 

This  method  of  preparation  is  called  "roasting." 


ANTIMONY  OXYCHLORIDE. 

ANTIMONI    OXYCHLORIDUM. 

(Algaroth's  Powder.) 
2SbOCl.Sb2O3=630.8. 

Prepared  by  pouring  a  solution  of  antimony  chloride  (see 
Antimony  Chloride  Solution  and  Antimony  Oxide)  into  a  large 
quantity  of  water.  The  directions  given  under  the  title  Antimony 
Oxide  down  to  and  including  the  washing  of  the  precipitated 
oxychloride  with  hot  water  may  be  followed  (the  treatment  of 
the  washed  precipitate  with  ammonia  being  omitted).  The  prod- 
uct is  then  dried  with  the  aid  of  heat. 

It  is  a  white,  insoluble  powder. 

ANTIMONYL-POTASSIUM  TARTRATE. 

ANTIMONI    ET   POTASSII   TARTRAS. 

[Tartar  Emetic.] 
2KSbOC4H4O6.H2O=662.42. 

Antimonous  oxide 4  parts 

Potassium  bitartrate   5  parts 

Water    50  parts 

Mix  the  oxide  and  the  cream  of  tartar  with  enough  water  to 
form  a  paste,  and  set  this  aside  for  twenty-four  hours.  Then  add 
the  remainder  of  the  water  and  boil  the  mixture  in  a  porcelain 
capsule  for  fifteen  minutes,  stirring  frequently,  and  replacing  the 
water  lost  by  evaporation.  Filter  while  hot,  evaporate  the  filtrate 


ANTIMONIC  SULPHIDE.  285 

to  30  parts,  and  set  it  aside  to  crystallize.    Wash  the  crystals  with 
a  little  cold  water,  and  then  dry  them  between  filter  paper. 

Reaction,     2KHC4H4O6+Sb2O3=2K(SbO)C4H4O6+H2O. 

Notes.  A  slight  excess  of  antimonous  oxide  is  used,  but  re- 
mains undissolved  and  is  filtered  away.  To  obtain  the  salt  in 
minute  crystals  the  solution  obtained  by  the  above  formula  may 
be  evaporated  down  to  27  parts  and  then  shaken  in  a  bottle  until 
cold,  when  the  greater  part  of  the  salt  will  separate.  The  mother 
liquor  will  yield  more  crystals,  but  after  two  or  three  crystalliza- 
tions it  becomes  quite  colored,  as  is  the  case  in  making  several 
other  tartrates. 

Description. — Small,  transparent  crystals,  or  white  powder, 
odorless,  having  a  sweet,  afterwards  disagreeable,  metallic  taste. 
Soluble  in  17  parts  of  water  at  15°,  and  in  3  parts  of  boiling  water. 
Insoluble  in  alcohol. 

The  colorless  crystals  become  white  or  opaque  on  exposure  to 
the  air. 


ANTIMONIC   SULPHIDE. 

ANTIMONI      PENTASULPHIDUM. 

(Stibium  Sulphuratum  Aurantiacnni. — "Golden  Sulphur et  of  An- 
timony.") 

Chiefly  Sb2S5=4OO. 

Purified  black  antimony  sulphide 18  parts 

Sublimed  sulphur   5  parts 

Sodium   hydroxide    13  parts 

Water   50  parts 

Sulphuric  acid,  distilled  water,  each  sufficient. 

Triturate  the  antimonous  sulphide  and  the  sulphur  together 
until  mixed ;  add  the  mixture  to  the  sodium  hydroxide  previously 
dissolved  in  the  water ;  boil  the  mixture  with  constant  stirring 
about  fifteen  minutes,  or  until  no  more  of  the  powder  dissolves. 
Filter,  evaporate  the  filtrate,  and  let  it  cool,  that  crystals  may 
form. 


286  ANTIMONIC  SULPHIDE. 

Rinse  the  crystals  hastily  with  a  little  weak  soda  solution,  and 
dry  them  by  pressing  them  between  bibulous  paper.  [These 
crystals  are  the  so-called  "Schlippe's  Salt"— Na3SbS4-f9H2O.] 

Dissolve  100  parts  of  these  crystals  in  400  parts  of  distilled 
water.  Filter,  if  necessary.  Dilute  the  filtrate  with  six  hundred 
parts  of  distilled  water,  and  pour  the  dilute  solution  slowly  and 
with  constant  stirring  into  a  mixture  of  thirty-six  parts  (by 
weight)  of  sulphuric  acid  and  six  hundred  parts  of  distilled 
water. 

Wash  the  precipitate  as  rapidly  as  possible,  by  affusion  and  de- 
cantation,  with  distilled  water,  let  drain,  express  the  remainder 
of  the  water,  and  dry  the  precipitate  with  the  aid  of  gentle  heat. 
Keep  it  in  a  tightly  corked  bottle,  protected  from  light. 

Reaction. 

4Sb2S3+4S2+  iSNaOH— 5Na3SbS4+3NaSbO3+9H2O ; 
then,  2Na3SbS4+3H2SO4-fioH2O 

=Sb2S5-f3Na2S04.  ioH20+3H2S. 

Notes.  The  direction  to  wash  the  crystals  of  Schlippe's  salt  is 
given  for  the  purpose  of  removing  sulpharsenate,  which  is  more 
readily  soluble,  and  a  little  sodium  hydroxide  is  added  to  the  wash- 
water  in  order  to  prevent  oxidation. 

The  sulphuric  acid  must  be  in  excess;  otherwise  the  product 
will  be  dark  colored. 

The  washing  must  be  done  with  distilled  water,  and  should  not 
be  long  continued.  Affusion  and  decantation  is  therefore  to  be 
preferred. 

Several  formulas  prescribe  an  excessive  proportion  of  sulphur 
— equal  weights  of  sulphur  and  antimony  sulphide. 

Description. — An  orange-red,  odorless,  insoluble  powder. 

This  preparation  is  identical  with  the  "sulphurated  antimony" 
of  the  British  Pharmacopoeia  and  with  the  old  "golden  sulphuret 
of  antimony."  It  is  redder  than  the  sulphurated  antimony  of  the 
Pharmacopoeia  of  the  United  States  and  the  Kermes  Mineral  of 
the  old  pharmacopoeias,  both  of  which  contain  Sb2S3  but  not 
Sb2S5. 


ANTIMONOUS    SULPHIDE.  287 

ANTIMONOUS  SULPHIDE. 

ANTIMONI    SULPHIDUM    NIGRUM. 


Native  antimony  trisulphide  (antimonite),  purified  by  fusion, 
and  as  free  from  arsenic  as  it  can  be  obtained,  constitutes  the 
"antimony  sulphide"  of  the  Pharmacopoeia. 

Description.  —  Dark  steel-gray,  striated  crystalline  masses,  of 
metallic  lustre,  forming  a  black  or  grayish-black  lustreless  pow- 
der when  reduced  to  a  very  fine  state  of  division  ;  odorless  ;  taste- 
less ;  insoluble  in  water  and  in  alcohol.  Soluble  in  strong  hydro- 
chloric acid  with  evolution  of  hydrogen  sulphide. 

Purified  Antimony  Sulphide. 

Antimony  sulphide   ....................   2  parts 

Water  of  ammonia  ....................    I  part 

Reduce  the  antimony  sulphide  to  a  very  fine  powder.  Separate 
the  coarser  particles  by  elutriation,  and,  when  the  finely  divided 
sulphide  has  been  deposited,  pour  off  the  water,  add  the  water  of 
ammonia,  and  macerate  for  five  days,  agitating  the  mixture  fre- 
quently. Then  let  the  powder  settle,  pour  off  the  water  of  am- 
monia, and  wash  the  residue  by  repeated  affusion  and  decantation 
of  water.  Finally,  dry  the  product  by  the  aid  of  heat. 

Note.  By  this  treatment  all  but  traces  of  arsenic  is  removed  as 
soluble  ammonium  sulph-arsenite. 

Description.  —  An  impalpable,  heavy,  grayish-black,  lustreless, 
odorless,  tasteless,  insoluble  powder. 

Sulphurated  Antimony. 

Chiefly  antimonous  sulphide  with  a  very  small  amount  of  anti- 
monous  oxide. 

Purified  antimony   sulphide  ............      i  part 

Solution  of  sodium  hydroxide  ..........    12  parts 

Diluted  sulphuric  acid,  sufficient. 


288  ANTIMONOUS    SULPHIDE. 

Mix  the  antimony  sulphide  with  the  solution  of  sodium  hydrox- 
ide and  30  parts  of  distilled  water,  and  boil  the  mixture  gently 
for  two  hours,  constantly  stirring,  and  occasionally  adding  dis- 
tilled water  so  as  to  preserve  the  same  volume.  Strain  the  liquid 
immediately  through  a  double  muslin  strainer,  and  drop  into  it, 
while  yet  hot,  diluted  sulphuric  acid  so  long  as  it  produces  a  pre- 
cipitate. 

Wash  the  precipitate  with  hot  distilled  water  until  the  washings 
are  at  most  but  very  slightly  clouded  by  test  solution  of  barium 
chloride;  then  dry  the  precipitate  at  25°  and  rub  it  to  a  fine  pow- 
der. 

Reaction. 

First,      Sb2S3+6NaOH=Na3SbO3+Na3SbS3-f  3H2O ;      then 
2Na3SbO3+3H2SO4=3Na2SO4+Sb2O3+3H2O,  and 
2Na3SbS3+3H2SO4=3Na2SO4+Sb2S3+3H2S. 

Notes.  The  antimony  sulphide  must  be  in  the  form  of  an  "im- 
palpable powder."  This  product  is  not  the  same  as  the  "sulphur- 
ated antimony"  of  the  British  Pharmacopoeia ;  the  B.P.  preparation 
consists  mainly  of  Sb2S5  (see  Antimonic  Sulphide)  ;  neither  is 
it  the  "Kermes  Mineral"  of  the  old  pharmacopoeias.  The  Phar- 
macopoeia of  the  United  States,  nevertheless,  gives  this  prepara- 
tion the  title  of  the  British  official  precipitated  antimony  sulphide 
as  well  as  the  synonym  "Kermes  Mineral." 

Description. — A  reddish-brown  or  brown-red  odorless,  taste- 
less, insoluble  powder.  It  is  redder  than  Kermes  Mineral,  but 
not  so  red  as  the  antimonic  sulphide  or  sulphurated  antimony  of 
the  British  Pharmacopoeia. 

Oxy sulphurated  Antimony. 
(KERMES  MINERAL.    KERMES  ANTIMONI.) 

Purified  antimony  sulphide I  part 

Sodium  carbonate  25  parts 

Put  the  sodium  carbonate,  together  with  250  parts  of  water, 
into  an  iron  pot,  and  heat  to  boiling.  Add  the  sulphide  and  con- 
tinue boiling  for  two  hours,  stirring  constantly,  and  replacing  the 


KERMES   MINERAL.  289 

water  lost  by  evaporation.  Filter,  as  rapidly  as  possible,  and 
while  still  hot,  into  a  warm  porcelain  dish  or  stone  jar  kept  in 
hot  water,  so  that  the  filtrate  will  cool  very  slowly. 

When  cold,  decant  the  clear  liquid  from  the  precipitate,  collect 
the  latter  at  once  on  a  filter,  and  wash  it  with  cold  distilled  water 
until  the  washings  no  longer  give  an  alkaline  reaction  on  test- 
paper,  or  until  the  washings  begin  to  be  colored. 

Then  press  the  precipitate  between  blotting  paper,  and  after- 
wards dry  it  in  a  dark  place  at  a  temperature  not  exceeding  30°  C. 
(86°  F.).  When  dry,  powder  it,  and  keep  it  in  tightly  closed 
bottles,  protected  from  light. 

Reaction. 

5Na2CO;!+6Sb,S3=NaSbO2+9NaSbS2+Sb2O3+5CO2, 
and  Na,CO3+Sb2O3=2NaSbO2+CO2. 

Notes.  The  product  consists  mainly  of  Sb2S3  with  some  Sb2O3. 
This  is  accounted  for  by  the  fact  that  the  hot  solution  of  sodium 
sulphantimonite  (NaSbS2)  is  capable  of  dissolving  a  considerable 
quantity  of  antimonous  sulphide,  which  deposits  on  cooling.  At 
the  same  time  it  requires  a  very  large  excess  of  sodium  carbonate 
to  prevent  the  separation  of  antimonous  oxide  and  sodium  of  an- 
timonite;  hence  the  quantity  of  sodium  carbonate  prescribed  is 
more  than  twenty  times  the  amount  required  by  theory.  Neverthe- 
less the  precipitation  of  antimonous  oxide  is  only  partially  pre- 
vented. If  the  proportion  of  sodium  carbonate  used  be  diminished 
the  product  contains  more  oxide.  The  large  quantity  of  water 
used  is  also  necessary  to  prevent  the  separation  of  an  undue  pro- 
portion of  oxide. 

The  boiling  should  not  be  continued  longer  than  the  prescribed 
period,  and  the  solution  must  not  be  allowed  to  cool  rapidly.  It 
is  best  to  let  the  temperature  fall  gradually  from  the  boiling  point 
down  to  about  40°  during  a  period  of  several  hours. 

If  the  solution  be  cooled  below  40°  the  precipitate  afterwards 
formed  contains  more  oxide.  Therefore  the  kermes  slowly  de- 
posited from  the  dilute  solution  during  the  slow  cooling  from  100° 
to  40°  is  all  that  can  be  obtained.  It  is  a  very  small  quantity,  and 
the  process  is  accordingly  attended  with  great  waste  of  material ; 
but  a  precipitated  antimonous  sulphide  obtained  in  any  other  ivay 
is  not  kermes. 

Vol.    11—19 


2QO  ARSENOUS   ACID. 

If  sodium  hydroxide  be  used  instead  of  the  carbonate,  the  prod- 
uct is  nearly  the  same  in  composition,  but  has  an  altogether 
different  appearance. 

Kermes  mineral  does  not  deserve  a  place  in  any  pharmacopoeia, 
and  very  few  pharmacopoeias  now  contain  it.  It  is  a  relic  of  the 
times  when  peculiar  physical  properties  due  to  extraordinary 
methods  of  preparation  were,  often  without  reason,  held  to  be 
indicative  of  extraordinary  medicinal  virtues. 

Description. — Prepared  carefully  in  strict  obedience  to  the  direc- 
tions given,  kermes  mineral  is  a  beautiful,  velvety,  dark  purplish- 
brown  powder.  Minute  crystals  of  antimonous  oxide  may  be  seen 
under  the  microscope  as  shining  particles  in  the  product. 

The  Pharmacopoeia  of  the  United  States  (1890)  gives  the 
synonym  "Kermes  Mineral"  to  the  antimonous  sulphide  precipi- 
tated from  a  solution  of  sodium  sulphantimonite  by  the  addition 
of  sulphuric  acid;  but  that  is  not  the  kermes  mineral  of  the  old 
pharmacopoeias. 

The  Norwegian  Pharmacopoeia  directs  the  preparation  of 
kermes  mineral  by  mixing  i  part  of  antimonous  oxide  with  nine 
parts  of  precipitated  sulphide. 


ARSENOUS   AGID    SOLUTION. 

LIQUOR    ACIDI    ARSENOSI. 

Arsenous   oxide 10  Gm 

Hydrochloric  acid 50  ml 

Distilled  water,  sufficient. 

Boil  the  arsenous  oxide  with  the  acid  diluted  with  250  ml  of  the 
water  until  dissolved.  Filter  the  solution,  pass  enough  distilled 
water  through  the  filter  to  make  the  product  measure  i  liter,  and 
mix  the  whole  well. 

Notes.  The  presence  of  hydrochloric  acid  materially  aids  the 
solution  of  the  arsenous  oxide.  When  dissolved  in  the  water  the 
oxide  is  probably  converted  into  arsenous  acid : 

As203+3H20=:2H3As03. 
This  preparation  was  formerly  erroneously  called  "solution  of 


ARSENOUS  IODIDE.  2QI 

chloride  of  arsenic;"  it   probably   contains  very  little  arsenous 
chloride. 

Description. — A  colorless   solution  with  an  acid  reaction.     It 
gives  a  bright  yellow  precipitate  with  hydrogen  sulphide. 

ARSENOUS    IODIDE. 

ARSENI    IODIDUM. 


Arsenic 3  parts 

Iodine 16  parts 

Triturate  until  finely  powdered  and  thoroughly  mixed.  Put 
into  a  flask  and  heat  gently  on  a  water-bath,  inclining  the  flask 
in  different  directions,  until  fusion  takes  place.  Pour  the  fused 
mass  upon  a  porcelain  slab  and  let  it  cool,  then  break  it  into 
pieces  and  keep  it  in  well  stoppered  bottles  in  a  cool  place. 

Description. — The  product  consists  of  glossy  orange-red  crys- 
talline masses  or  scales  having  an  odor  of  iodine.  It  decomposes 
on  exposure  to  air  and  light. 

Solution  of  Arsenic  and  Mercuric  Iodide. 
DONOVAN'S  SOLUTION. 

Arsenic  iodide I  part 

Mercuric  iodide i  part 

Distilled  water,  sufficient. 

Triturate  the  iodides  with  15  parts  of  distilled  water,  until  dis- 
solved. Filter  the  liquid  and  pass  enough  distilled  water 
through  the  filter  to  make  the  product  weigh  100  parts. 

Keep  the  product  in  a  dark  place. 

Notes.  No  chemical  reaction  takes  place  in  dissolving  the  two 
iodides  together ;  but  the  mercuric  iodide  is  soluble  in  the  solution 
of  arsenic  iodide,  although  almost  insoluble  in  water. 

The  arsenic  iodide  must  not  contain  free  iodine.  The  prepara- 
tion does  not  remain  unchanged  a  long  time.  It  must  be  odorless 
and  only  pale  yellowish — not  having  any  odor  of  iodine  nor  a 


ARSENOUS  OXIDE. 

reddish  color.     As  soon  as  it  acquires  the  odor  of  iodine  or  a 
reddish  color  it  should  be  thrown  away. 

Description. — A  clear  pale  yellowish  liquid  without  odor,  but 
having  a  nauseous  metallic  taste. 


ARSENOUS   OXIDE. 

ARSENI  OXIDUM. 


(Acidum  Arsenosum  of  the  Pharmacopoeias.} 

A  heavy  solid,  occurring  either  in  transparent  colorless  glassy 
masses,  or  white  porcelain-like,  or  in  white  powder;  very 
poisonous. 

For  medicinal  uses  it  must  be  in  extremely  fine  powder.  It 
may  be  powdered  by  trituration  in  a  porcelain  mortar;  but  it 
should  be  kept  moist  with  alcohol  while  triturated  to  prevent  the 
rising  of  the  poisonous  dust. 

Forms  a  permanent  solution  in  80  parts  of  water.  Dissolves 
slowly  unless  the  solution  is  aided  by  heat. 


BARIUM    ACETATE. 

BARII    ACETAS. 

Ba(C2H302)2.H20=273. 

Barium  carbonate  .....................   10  parts 

Acetic  acid  (36%)  ....................    17  parts 

Water  ...............................    10  parts 

Dissolve,  filter,  and  evaporate  to  crystallization.     Dry  the  crys- 
tals in  a  desiccator  over  sulphuric  acid,  or  with  the  aid  of  heat. 
Keep  the  product  in  a  tightly  closed  bottle. 

Description.  —  White,  deliquescent,  odorless;  readily  soluble. 


BARIUM  BROMIDE.  293 

BARIUM    BROMIDE. 

BARII    BROMIDUM. 

BaBr2.2H2O=332. 

This  salt  is  prepared  by  saturating  hydrobromic  acid  with 
barium  carbonate,  filtering  the  solution,  and  evaporating  to  crys- 
tallization. 

It  may  also  be  made  from  barium  hydroxide  with  ammonium 
bromide  in  the  same  manner  as  calcium  bromide  is  prepared  from 
lime  and  ammonium  bromide. 

Another  method  is  analogous  to  that  employed  for  the  prepara- 
tion of  ammonium  bromide  from  bromide,  of  iron,  the  materials 
bei'ng  ferroso-ferric  bromide  and  barium  hydroxide. 

Description.  —  Colorless  crystals,  or  a  white  granular  salt  ;  odor- 
less; taste  acrid,  nauseous.  Readily  soluble  in  water  and  in 
alcohol. 

BARIUM    CARBONATE. 

BARII    CARBONAS. 


Barium  nitrate  .......................  100  parts 

Ammonium  carbonate  .................  37  parts 

Ammonia  water  (10%  of  H3N)  .......  80  parts 

Water. 

Dissolve  the  barium  nitrate  in  600  parts  of  water,  and  filter  if 
necessary.  Dissolve  the  ammonium  carbonate  in  80  parts  of 
water,  and  filter  if  required.  Warm  the  barium  nitrate  solution  to 
50°  and  add  it  gradually  to  the  ammonium  carbonate  solution, 
stirring  well.  Let  the  mixture  become  cold.  Then  add  ammonia 
water  until  the  mixture  acquires  a  decided  ammonlacal  odor.  Stir 
well.  Let  settle.  Decant  the  liquid.  Wash  the  precipitate  until 
the  washings  are  free  from  ammonium  salts  (as  indicated  by  their 
being  no  longer  affected  by  sodium  cobaltic  nitrate  test-solution). 
Dry  the  precipitate  with  the  aid  of  heat. 


294  BARIUM   CHLORIDE. 

Reaction. 

Ba  ( NO3 )  2+  ( H4N)  2CO3=BaCO3+2H4NNO3. 

Notes.  Ammonium  carbonate  is  prescribed  instead  of  potas- 
sium or  sodium  carbonate,  because  it  is  scarcely  possible  to  re- 
move all  potassium  or  sodium  salt  from  the  precipitated  barium 
carbonate,  while  ammonium  salt  is  easily  removed.  Ammonia 
water  is  added  not  only  to  convert  the  ordinary  carbonate  into 
the  normal  salt,  but  also  because  the  barium  carbonate  is  some- 
what soluble  in  ammonium  nitrate  solution,  but  not  in  the  am- 
moniacal  liquid  obtained  by  the  addition  of  an  excess  of  am- 
monia. 

Description. — A  heavy,  white,  insoluble,  odorless  and  tasteless 
powder.  Completely  soluble  in  nitric  acid  and  in  hydrochloric 
acid. 

Other  Methods. 

From  heavy  spar  (barium  sulphate)  the  carbonate  of  barium 
can  be  obtained  by  heating  to  redness  an  intimate  mixture  made 
of  10  parts  of  powdered  heavy  spar,  2  parts  of  powdered  charcoal, 
and  5  parts  of  potassa,  and  then  washing  the  fused  mass  with 
water,  when  the  undissolved  residue  is  barium  carbonate. 

BaSO4+2KOH+2C==BaCO3+K2S+H2O-hCO2. 

The  impure  native  barium  carbonate  called  "witherite"  may  be 
converted  into  chloride  as  described  under  the  title  Barium  Chlor- 
ide, and  the  pure  carbonate  then  made  from  the  chloride  by  pre- 
cipitation with  ammonium  carbonate. 

BARIUM    CHLORIDE. 

BARII    CHLORIDUM. 

BaCl2.2H2O— 243.56. 

Powdered  witherite 10  parts 

Hydrochloric  acid  (31.9%  of  HC1) n  parts 

Barium  sulphide. 
Water. 

Mix  the  witherite  thoroughly  with  its  own  weight  of  water  in 


BARIUM  CHLORIDE.  295 

a  porcelain  dish.  Then  add,  gradually,  the  hydrochloric  acid 
previously  mixed  with  10  parts  of  water,  stirring  well,  waiting 
after  each  addition  of  the  dilute  acid  until  the  effervescence  has 
subsided  before  adding  more.  When  the  interaction  becomes 
tardy,  heat  the  dish  over  the  water-bath  to  facilitate  the  satura- 
tion of  the  acid.  When  all  of  the  acid  has  been  added, 
evaporate  the  unfiltered  liquid  to  dryness,  and  heat  the  dry 
residue  at  about  100°  for  half  an  hour.  Then  add  50  parts  of 
boiling  water ;  stir  well,  continuing  the  heating  and  stirring  about 
five  minutes.  Filter.  Add  to  the  filtrate  a  solution  of  barium 
sulphide  until  no  further  precipitation  is  produced  by  it.  Filter 
again.  Acidify  the  filtrate  with  hydrochloric  acid  so  that  it  just 
shows  a  distinct  acid  reaction  on  litmus  paper.  Then  evaporate 
the  solution  to  the  density  of  about  1.3  and  set  it  aside  in  a  cool 
place  to  crystallize. 

Recrystallize  the  salt  two  or  three  times,  as  may  be  necessary. 

Reaction.     BaCO3+2HCl=BaCl2+H2O+CG2. 

Notes.  The  mineral  "witherite"  is  an  impure  native  barium 
carbonate,  containing  varying  amounts  of  calcium,  strontium  and 
iron  compounds  together  with  other  mineral  substances.  A  very 
large  excess  of  witherite  must  necessarily  be  used,  because  much 
of  it  may  consist  of  substances  other  than  barium  carbonate,  and  it 
is  further  requisite,  that,  after  the  saturation  of  the  acid,  a  con- 
siderable amount  of  barium  carbonate  shall  still  remain  in  order 
that,  during  the  evaporation  of  the  solution  to  dryness,  the  iron 
and  calcium  may  be  precipitated.  The  remaining  iron  and  any 
other  heavy  metals  present  are  removed  by  precipitation  with 
barium  sulphide,  which  must,  however,  be  employed  with  great 
caution  to  avoid  using  an  excess.  The  final  solution  still  contains 
chlorides  of  the  alkali  metals  and  of  calcium  and  strontium,  which 
must  be  removed  by  re-crystallization  of  the  barium  chloride 
which  is  less  freely  soluble  than  the  others,  so  that  the  latter 
remain  in  the  mother  liquors.  The  concentrated  solution  of 
barium  chloride  can  also  be  mixed  with  alcohol,  which  precipi- 
tates the  salt  while  the  calcium  and  strontium  chlorides  remain 
in  solution. 

A  pure  barium  chloride  may,  of  course,  be  at  once  obtained 
by  saturating  pure  hydrochloric  acid  with  pure  barium  carbonate. 


296  BARIUM    CH  ROM  ATE. 

Description. — Colorless  crystals,  soluble  in  3  parts  of  water  at 
10°,  in  2  parts  at  72°,  and  in  1.6  parts  of  boiling  water.  The 
solution  is  neutral. 


BARIUM    CHROMATE. 

BARII    CHROMAS. 


Barium  acetate  ........................   50  parts 

Potassium  dichromate  ........  ..........   27  parts 

Water. 

Dissolve  the  dichromate  in  75  parts  of  hot  water  and  filter. 
Dissolve  the  barium  acetate  also  in  75  parts  of  water  and  filter. 
Add  the  latter  solution  to  the  former,  stirring  well.  Wash  the 
precipitate  by  affusion  and  decantation  of  cold  water.  Collect, 
drain  and  dry  it. 

Reaction. 

2Ba(C2H302)2.H20+K2Cr207 

=2BaCrO4-f2KC2H3O24-2HC2H3O2. 

Description.  —  An  insoluble  lemon-yellow  powder,  usetf  as  a 
pigment. 

BARIUM    DIOXIDE. 

BARII    DIOXIDUM. 

BaO2=i69. 

When  a  current  of  air  is  conducted  over  barium  oxide  heated 
at  450°  C.  the  oxide  is  converted  into  dioxide.  The  barium  di- 
oxide is  employed  in  the  preparation  of  hydrogen  dioxide. 

Description.  —  A  heavy,  grayish-white,  or  pale  yellowish-  white, 
coarse  powder.  Odorless  and  tasteless.  Nearly  insoluble  in  cold 
water. 


BARIUM    NITRATE.  297 

BARIUM    NITRATE. 

BARII    NITRAS. 

Ba(NO3)2=26i. 

Powdered  witherite 16  parts 

Nitric  acid  (68%  of  HNO3) 15  parts 

Water. 

Mix  the  witherite  thoroughly  in  a  porcelain  dish  with  its  own 
weight  of  water.  Dilute  the  nitric  acid  with  its  own  weight  of 
water.  Add  the  diluted  acid,  in  small  portions,  to  the  witherite, 
stirring  well  and  waiting  after  each  addition  until  the  efferves- 
cence has  subsided  before  adding  the  next  portion  of  acid.  When 
about  one-half  of  the  acid  has  been  added,  place  the  dish  over  a 
water-bath,  apply  heat,  add  about  40  parts  of  hot  water,  stir  well 
and  then  proceed  with  the  addition  of  the  remainder  of  the  nitric 
acid,  in  small  portions,  as  before,  stirring  well.  Evaporate  the 
contents  of  the  dish  to  dryness.  Add  to  the  dry  residue  60  parts 
of  boiling  water,  stir  well,  and  continue  heating  the  mixture  at  90° 
or  over  for  half  an  hour.  Filter.  Acidify  with  nitric  acid. 
Evaporate  the  filtrate  to  crystallization.  Recrystallize  two  or 
three  times,  as  may  be  necessary. 

Reaction.     BaCO3+2HNO3=Ba  ( NO3 )  2+H2O-fCO2. 

Notes.  The  impure  barium  carbonate  is  used  in  large  excess 
(see  notes  under  Barium  Chloride).  Iron  is  precipitated  by  the 
excess  of  barium  carbonate.  The  nitrates  of  strontium  and  cal- 
cium remain  in  the  mother-liquors  when  the  product  is  re-crys- 
tallized. 

The  crystallization  proceeds  most  satisfactorily  when  the  acidi- 
fied solution  saturated  at  about  80°  to  90°  is  slowly  cooled. 

Pure  barium  carbonate  and  nitric  acid  readily  produce  a  pure 
barium  nitrate. 

Description. — Colorless  or  white  crystals.  Soluble  in  7  parts 
of  water  at  10°  ;  in  9.2  parts  at  20°  ;  in  5  parts  at  60°  ;  and  in  a 
little  less  than  3  parts  of  boiling  water. 


298  BARIUM    HYDROXIDE. 

BARIUM    HYDROXIDE. 

BARII    HYDROXIDUM. 

Ba(OH)2=i7i. 

Barium  chloride  ....................    1,000  parts 

Sodium  hydroxide  ..................       310  parts 

Water. 

Dissolve  the  barium  chloride  in  2,000  parts  of  hot  water  and 
the  sodium  hydroxide  in  840  parts  of  water.  Mix  the  solutions. 
Heat  to  boiling.  Filter  while  hot.  Set  aside  to  crystallize. 
Recrystallize  the  hydroxide  twice  from  hot  water.  Drain  the 
crystals  on  a  platinum  cone  by  means  of  a  filter  pump.  Preserve 
the  product  in  tightly  stoppered  bottles. 

BARIUM    OXIDE. 

BARII    OXIDUM. 

BaO=i53. 

Prepared  by  heating  barium  nitrate  to  white  heat  in  a  Hessian 
crucible  covered  with  a  fire  clay  cover.  The  Roessler  furnace 
may  be  used  for  this  purpose  when  the  quantity  is  small. 

Properties.  Grayish-white,  porous  pieces,  forming  barium  hy- 
droxide with  water. 

BISMUTH;    PURIFIED. 

BISMUTHUM    PURIFICATUM. 


Commercial  bismuth  .............  .......      I  part 

Potassium   nitrate  .....................    1  1  parts 

Triturate  the  bismuth  with  ten  parts  of  the  potassium  nitrate 
until  the  two  substances  are  well  -mixed.  Heat  the  mixture  in 
a  crucible  to  complete  fusion,  stir  uninterruptedly  with  a  clay 
rod  (or  pipe-stem)  and  keep  the  mass  in  a  state  of  fusion  for  at 
least  half  an  hour.  Then  pour  the  fused  mass  into  a  vessel  of 


BISMUTH.  299 

hot  water.  Dry  the  undissolved  residue,  consisting  of  bismuth 
and  some  bismuth  oxide,  mix  it  well  with  i  part  of  potassium 
nitrate,  and  fuse  the  mixture  as  before,  and  separate  the  slag  from 
the  insoluble  bismuth  oxide  and  the  ingot  of  metal. 

Notes.  Commercial  bismuth  contains  arsenic,  sulphur  and 
selenium.  They  are  converted  into  arsenate,  sulphate  and  selenate 
of  potassium  by  fusion  with  the  potassium  nitrate.  These  salts 
together  with  the  excess  of  potassium  nitrate  are  water-soluble, 
and  thus  separated  by  the  water.  The  bismuth  is  fused  together 
in  one  lump.  Any  bismuth  oxide  formed  remains  in  pulverulent 
form  when  the  slag  of  salts  has  been  washed  off,  and  can  be 
recovered. 

Another  Method. 

Bismuth  2  parts 

Sodium  nitrate I  part 

Solution    of    sodium    hydroxide    (5%    of 

NaOH) 9  parts 

Water. 

Mix  the  bismuth  and  sodium  nitrate  and  heat  the  mixture  in 
an  iron  dish  at  low  red  heat.  When  the  mass  begins  to  swell 
,stir  uninterruptedly  with  an  iron  spatula  for  about  an  hour  or 
until  the  metal  is  finely  divided  and  thus  scarcely  distinguishable 
in  the  mixture.  Then  remove  the  dish  from  the  source  of  heat, 
and  add  to  the  half-cooled  contents  the  solution  of  sodium  hydrox- 
ide. Heat  the  mixture  to  boiling,  stirring  well.  Transfer  the 
whole  to  a  paper  filter,  let  the  liquid  run  off,  wash  the  finely 
divided  bismuth  remaining  on  the  filter,  and  dry  it. 

Some  bismuth  oxide  is  mixed  with  the  metal  thus  purified, 
and  it  is  possible  that  some  bismuth  arsenate  may  also  remain 
with  the  product. 

BISMUTH    BENZOATE. 

BISMUTHI    BENZOAS. 

Freshly  prepared  and  still  moist  bismuth  hydroxide  is  digested 
at  about  80°  C.  with  an  excess  of  benzoic  acid  mixed  with  ten 
times  its  weight  of  water  in  a  porcelain  dish  over  a  water-bath 
for  about  half  an  hour. 


3<DO  BISMUTH  BENZOATE. 

[The  quantity  of  bismuth  hydroxide  required  for  100  Gm  of 
benzoic  acid  is  about  that  corresponding  to  175  Gm  of  bismuthous 
oxide.] 

The  insoluble  product  (which  is  said  to  yield  about  64  to  65 
per  cent  of  bismuthous  oxide  on  ignition)  is  washed  as  rapidly 
as  possible  with  cold  water,  and  dried  at  a  temperature  not  ex- 
ceeding 80°  C. 

Another  Method. 

Crystallized  normal  bismuth  nitrate 20  parts 

Glycerin 30  parts 

Sodium  benzoate 20  parts 

Distilled  water,,  sufficient. 

Crush  and  then  powder  the  bismuth  nitrate  in  a  deep  porcelain 
dish.  Pour  upon  it  the  glycerin  and  stir  well  together.  Place 
the  dish  over  a  water-bath  and  heat  until  the  bismuth  nitrate  is 
dissolved.  Add  65  parts  of  distilled  water. 

Dissolve  the  sodium  benzoate  in  one  liter  of  water  at  a  tem- 
perature of  about  40°  to  50°  C. 

Add  the  bismuth  solution  gradually  to  the  solution  of  sodium 
benzoate,  stirring  well.  Let  the  precipitate  subside,  decant  the 
mother-liquor,  and  wash  the  precipitate  with  warm  water  (40° 
— 50°  C.)  by  decantation  until  the  washings  give  no  further 
reaction  for  nitrate.  Dry  the  product,  first  at  the  ordinary  tem- 
perature and  finally  at  not  over  80°  C.  Reduce  it  to  fine  powder. 

Description. — A  white,  amorphous,  odorless  and  tasteless  pow- 
der, insoluble  in  water.  Decomposed  by  hydrochloric  acid  or  by 
nitric  acid  with  the  separation  of  benzoic  acid. 


BISMUTH    CITRATE. 

BISMUTHI    CITRAS. 

BiC6H507=397. 

Bismuth  subnitrate 10  parts 

Citric  acid 7  parts 

Boil  them  with  40  parts  of  distilled  water  until  a  drop  of  the 
mixture  yields  a  clear  solution  with  ammonia  water.     Add  500 


BISMUTH   CITRATE.  30 1 

parts  of  distilled  water,  stir  well,  and  then  set  the  mixture  aside 
to  settle.  Decant  the  acid  supernatant  liquid,  and  wash  the  pre- 
cipitate, first  by  decantation  and  afterwards  on  a  filter,  until  the 
washings  are  tasteless.  Dry  the  product  by  moderate  heat. 

Reaction. 
OBiN03.H20+H3C6H507.H20=BiC6H507+HN03+3H20. 

Notes.  Citrate  of  bismuth  is  insoluble  in  water,  and  nearly  so 
in  the  dilute  nitric  acid  formed  by  the  reaction  taking  place  in 
this  process.  Subnitrate  of  bismuth  is  insoluble  in  ammonia 
water,  but  the  citrate  is  soluble  in  it,  and  hence  the  reaction  is 
known  to  have  been  completed  when  the  turbid  liquid  is  cleared 
by  ammonia  water. 

Another  Method. 

Subnitrate  of  bismuth 22  Gm 

Citric   acid 16  Gm 

Sodium  bicarbonate 32  Gm 

Nitric  acid,  44  ml,  or  sufficient. 
Distilled  water,  sufficient. 

Heat  the  subnitrate  of  bismuth  with  the  nitric  acid  until  dis- 
solved. Add  a  little  water,  with  constant  stirring,  until  the 
cloudiness  produced  by  the  water  no  longer  rapidly  disappears. 
Dissolve  the  sodium  bicarbonate  in  480  ml  of  distilled  water,  add 
the  citric  acid,  boil  until  effervescence  ceases,  and  then  add  this 
solution  to  the  clear  (or  only  faintly  opalescent)  solution  of  nitrate 
of  bismuth  until  no  further  precipitate  is  produced.  Heat  the 
mixture  to  boiling,  stirring  occasionally.  Set  aside  to  cool. 
When  cold,  filter,  and  wash  the  precipitate  until  all  free  nitric 
acid  has  been  removed.  Dry  the  product  by  water-bath  heat. 

Reaction.  Bismuth  nitrate  is  formed  by  the  solution  of  the 
subnitrate  in  nitric  acid ;  the  citric  acid  and  sodium  bicarbonate 
yield  sodium  citrate.  The  reaction  between  these  salts  is: 

Na3C6H507+Bi  ( NO, )  3=BiCcH5O7+3NaNO3. 

But  nitric  acid  is  used  in  excess,  and  sodium  bicarbonate  is 
also  used  in  excess,  and  the  excess  of  acid  on  the  one  hand  is 
nearly  neutralized  by  the  excess  of  alkali  on  the  other. 


3O2  BISMUTH    HYDROXIDE. 

Description. — A  white,  odorless  and  tasteless  powder,  readily 
soluble  in  ammonia  water,  but  insoluble  in  water  and  in  alcohol. 
Soluble  in  solutions  of  alkali  citrates. 


Bismuth  and  Ammonium  Citrate. 

BISMUTHI    ET    AMMONII    CITRAS. 

Citrate  of  bismuth I  part 

Water  of  ammonia,  sufficient. 

Mix  the  citrate  of  bismuth  with  two  parts  of  distilled  water  to 
a  smooth  paste,  and  gradually  add  water  of  ammonia  until  the 
salt  is  dissolved,  and  the  liquid  has  a  neutral  or  only  faintly 
alkaline  reaction.  Then  filter  the  solution,  evaporate  it  to  a  syrupy 
consistence,  spread  it  on  plates  of  glass,  and  dry  it  in  scales.  Keep 
the  product  in  small,  well  stoppered  bottles,  protected  from  light. 

Description. — Small  scales,  soluble  in  water.  Odorless.  Taste 
slightly  acidulous  and  slightly  metallic.  On  being  kept  for  some 
time  it  becomes  only  partially  soluble  in  water;  but  the  addition 
of  ammonia  effects  complete  solution. 

BISMUTH    HYDROXIDE. 

BISMUTHI    HYDROXIDUM. 

Bi(  OH)  3=26o. 

Crystallized  normal  bismuth  nitrate 10  Gm 

Nitric  acid 13  Gm 

Distilled  water,  ammonia  water,  each  sufficient. 

Dissolve  the  bismuth  nitrate  in  'the  nitric  acid  and  100  Gm  of 
water  previously  mixed.  Precipitate  with  ammonia  in  excess, 
by  pouring  the  bismuth  solution  gradually  and  with  constant  stir- 
ring into  35  Gm  of  ammonia  water.  Decant  the  liquid  from  the 
precipitate.  Add  to  the  precipitate  100  Gm  of  distilled  water 
mixed  with  10  Gm  of  ammonia  water  and  let  the  mixture  stand 
for  a  few  hours,  to  decompose  any  subnitrate  which  may  be  con- 
tained in  the  precipitate.  Wash  the  product  by  affusion  and 
decantation  of  cold  distilled  water  until  the  washings  give  no 


BISMUTH    NITRATE.  303 

further  reaction  for  nitrate  and  leave  no  residue  on  evaporation. 
Dry  the  product  without  heat. 

Reaction. 

OBiN03.H20+H4NOH=H4NN03+Bi(OH)3. 
Description. — A  white,  fine,  odorless  and  tasteless  powder. 

BISMUTH    NITRATE. 

BISMUTHI    NITRAS. 

(Trisnitrate  of  Bismuth.) 

Bi(N03)3.5H20=484. 

Proceed  as  in  the  formula  for  making  subnitrate  of  bismuth 
up  to  the  point  where  the  precipitated  subcarbonate  has  been  re- 
dissolved  in  nitric  acid.  Evaporate  this  solution  to  crystallization. 
Dry  the  crystals  by  gently  pressing  them  between  white  filter 
paper,  and  at  once  put  them  in  a  glass  stoppered  bottle. 

Description. — The  salt  is  in  large,  transparent  crystals,  colorless 
if  pure.  Decomposed  by  water ;  soluble  in  dilute  nitric  acid,  and 
in  glycerin,  also  in  glacial  acetic  acid. 

Glycerite  of  Bismuth  Nitrate. 

Normal  bismuth  nitrate I  part 

Glycerin  8  parts 

Powder  the  crystals  by  trituration  in  a  mortar.  Then  add  the 
glycerin,  all  at  once,  and  stir  until  the  salt  has  dissolved. 

Notes.  If  the  crystals  are  triturated  with  the  glycerin,  espe- 
cially with  a  small  quantity  of  glycerin,  there  is  danger  that  nitro- 
glycerin  may  be  formed  and  explosion  result. 

The  solution  is  used  for  preparing  certain  other  bismuth  prep- 
arations by  double  decomposition,  as  the  oleate,  salicylate,  and 
valerate. 


304  BISMUTH  OLEATE. 

BISMUTH    OLEATE. 

BISMUTHI   OLEAS. 

Bi(C18H3302)3=io5. 

Normal  bismuth  nitrate 20  Gm 

White  Castile  soap,  in  fine  powder 32  Gm 

Put  the  crystals  of  normal  nitrate  of  bismuth  into  a  mortar, 
powder  the  salt,  and  then  add,  all  at  once,  100  ml  of  glycerin; 
stir  occasionally,  avoiding  friction  or  pressure,  until  the  nitrate 
is  dissolved,  which  will  be  accomplished  in  a  few  hours.  Dissolve 
the  soap  in  1,500  ml  of  water,  and  then  add  slowly  the  solution 
of  nitrate  of  bismuth.  Warm  the  mixture,  reject  the  watery 
mother-liquor,  and  wash  the  oleate  twice  with  warm  distilled 
water. 

Reaction. 

Bi(N03)3+3NaC18H3302 

=Bi(C18H3302)3+3NaN03. 

Notes.  The  normal  nitrate  of  bismuth  is  to  be  powdered  before 
adding  the  glycerin,  and  the  glycerin  is  added  all  at  once  to  prevent 
possible  explosion  of  nitro-glycerin,  which  might  be  formed. 
This  oleate  must  be  fused  by  very  gentle  heat,  over  a  water-bath, 
to  get  rid  of  the  last  portions  of  water.  The  yield  is  about  36 
Gm,  and  the  product  is  a  white  or  yellowish  white  ointment  con- 
taining about  20  per  cent  of  bismuth. 

BISMUTH    OXIDE. 

BISMUTHI    OXIDUM. 

Bi2O3=466. 

Bismuth   subnitrate I  part 

Solution    of    sodium    hydroxide    ($%    of 

'   NaOH) 4  parts 

Mix  in  a  porcelain  dish  and  boil  the  mixture  for  ten  minutes. 


BISMUTH    SALICYLATE.  305 

Set  it  aside  to  settle.     Wash  the  precipitate  with  hot  water  sev- 
eral times.     Dry  it. 

Reactior 

2BiONO8.H2O+2NaOH=Bi2Os+2NaNO8H-2H2O. 
Description. — A  fine,  soft,  white,  odorless  and  tasteless  powder. 

BISMUTH    SALICYLATE. 

BISMUTHI    SALICYLAS. 

Prepared  by  double  decomposition  from  normal  bismuth  nitrate 
(59  parts)  and  sodium  salicylate  (51  parts).  The  nitrate  of  bis- 
muth is  dissolved  in  glycerin,  and  this  solution  gradually  added 
to  a  strong  solution  of  the  sodium  salicylate  in  water. 

Another  Method. 

Salicylic  acid  is  mixed  with  ten  times  its  weight  of  water  in  a 
porcelain  dish ;  bismuth  hydroxide,  recently  prepared  and  not 
dried,  is  added,  and  the  mixture  heated  at  about  80°  C.  The« 
salicylic  acid  must  be  used  in  excess,  and  the  liquid  must  at  the  end 
remain  acid  in  reaction.  Continue  heating  the  mixture  for  half  an 
hour,  stirring  constantly.  Let  it  cool.  Wash  the  precipitate  on 
a  strainer  or  in  a  paper  filter,  according  to  the  quantity  operated 
upon,  with  cold  distilled  water,  as  rapidly  as  practicable,  and  dry 
the  product  at  not  over  80°  C. 

Description. — Salicylate  of  bismuth  is  of  indefinite  composition. 
It  consists  of  a  white,  odorless  powder,  almost  entirely  insoluble 
in  water,  but  soluble  in  nitric  acid  or  hydrochloric  acid  with  sep- 
aration of  salicylic  acid. 

The  preparation  yields  all  of  its  salicylic  acid  to  boiling  alcohol, 
or  to  cold  ether. 

It  should  contain  an  amount  of  bismuth  corresponding  to  about 
61  per  cent  of  bismuthous  oxide. 

Vol.    11—20 


306  BISMUTH    SUBCARBONATE. 

BISMUTHYL    CARBONATE. 

BISMUTHI    SUBCARBONAS. 

[Sub carbonate  of  Bismuth.} 

(BiO)2CO3.H20^526. 

Bismuth,  in  small  pieces 50  Gm 

Nitric   acid 150  ml 

Ammonia  water 125  ml 

Sodium  carbonate 250  Gm 

Mix  800  ml  of  the  nitric  acid  with  100  ml  of  distilled  water  in  a 
capacious  glass  vessel,  add  the  bismuth,  and  set  aside  for  twenty- 
four  hours 'to  dissolve.  Dilute  the  solution  with  250  ml  of  dis- 
tilled water  (until  permanent  turbidity  results),  stir  well  again, 
set  the  liquid  aside  for  twenty-four  hours,  and  then  filter.  Di- 
lute the  filtrate  by  gradually  adding  to  it  1,600  ml  of  distilled 
water,  and  mixing  well.  Now  add,  slowly,  the  ammonia  water 
through  a  small  siphon,  stirring  constantly  and  actively.  Trans- 
fer the  whole  to  a  wetted  muslin  strainer,  and  let  drain.  When 
the  liquid  has  drained  off  pour  upon  the  precipitate  800  ml  of  dis- 
tilled water,  mixing  well,  and  then  let  drain  again.  Now  transfer 
the  precipitate  to  a  suitable  vessel,  add  the  remainder  of  the  nitric 
acid,  and,  when  all  has  dissolved,  also  add  gradually  100  ml  of 
distilled  water,  and  set  the  solution  aside  for  twenty-four  hours. 
Then  filter. 

Dissolve  the  sodium  carbonate  in  300  ml  of  distilled  water,  with 
the  aid  of  heat,  filter  the  solution,  and  set  it  aside  until  cold. 
Now  pour  the  cold  solution  of  bismuth  nitrate  very  slowly  into 
the  solution  of  sodium  carbonate,  with  constant  and  brisk  stir- 
ring. Transfer  the  whole  to  a  wetted  muslin  strainer,  and,  after 
draining  thoroughly,  wash  the  precipitate  with  distilled  water,  as 
expeditiously  as  practicable,  until  the  washings  become  tasteless. 
Lastly,  press  out  the  moisture  as  far  as  practicable,  dry  the  pre- 
cipitate on  bibulous  paper,  or  on  muslin,  at  a  gentle  heat,  and 
then  powder  it  by  rubbing  it  through  a  fine  sieve  by  means  of  a 
soft  brush. 

Reaction.     First  a  solution  of  bismuthous  nitrate  is  made: 
Bi-f  4HNO3=Bi  ( NO,,)  3+2H2O+NO. 


BISMUTH    SUBCARBONATE.  307 

This  is  poured  into  a  large  quantity  of  water  containing  am- 
monia, whereby  bismuthyl  nitrate  is  thrown  down,  the  ammonia 
being  added  to  neutralize  the  free  nitric  acid  so  as  to  prevent  it 
from  retaining  any  bismuth  nitrate  in  the  liquid.  Then  the  pre- 
cipitate is  redissolved  in  nitric  acid  to  form  again  the  Bi(NO3)3. 

Finally,  2Bi(NO3)3+3Na2CO3.H2O 

=  ( BiO )  2C03.H20+6NaN03+2CO2. 

Notes.  As  the  bismuth  usually  contains  arsenic  the  acid  solu- 
tion first  prepared  contains  bismuth  arsenate ;  when  the  liquid 
is  diluted  with  water  until  permanently  somewhat  turbid,  the 
arsenical  salt  precipitates  before  the  bismuthyl  nitrate  does,  and 
hence,  after  twenty-four  hours'  rest,  most  of  the  arsenate  is 
found  deposited  as  a  white  precipitate,  and  is  then  filtered  away. 
The  rest  of  the  arsenic  remains  in  the'  mother-liquor  after  the 
precipitation  of  the  bismuth  nitrate  with  ammonia,  as  ammonium 
arsenate.  See  also  the  notes  under  the  title  Bismuthyl  Nitrate. 

Description. — A  soft,  white  or  pale  yellowish,  odorless  and  taste- 
less powder,  which  becomes  converted  into  oxide  by  heat.  It  is 
quite  insoluble  in  water,  but  should  give  a  clear  solution  with 
nitric  acid. 

Another  Method. 

Purified  bismuth,  in  small  pieces 100  Gm 

Nitric  acid 200  ml 

Ammonium   carbonate 300  Gm 

Distilled  water,  sufficient. 

Mix  the  nitric  acid  with  150  ml  of  distilled  water,  and  add  the 
bismuth  in  successive  portions.  When  effervescence  has  ceased, 
apply  for  ten  minutes  a  temperature  approaching  that  of  ebulli- 
tion. Then  decant  the  solution  from  any  insoluble  matter  that 
may  be  present.  Evaporate  the  solution  until  it  is  reduced  to  100 
rnl,  and  add  this  in  small  quantities  at  a  time  to  a  cold  filtered 
solution  of  the  ammonium  carbonate  in  2  liters  of  distilled  water, 
stirring  constantly  during  the  admixture.  Collect  the  precipitate 
on  a  filter  and  wash  it  with  distilled  water  until  the  washings 
pass  tasteless.  Remove  now  as  much  of  the  adhering  water  as 
can  be  separated  from  the  precipitate  by  slight  pressure  with  the 


308  BISMUTH    SUBGALLATE. 

hands,  and  finally  dry  the  product  at  a  temperature  not  exceeding 
60.  °  5  C. 

Description. — A  soft,  white,  odorless  and  tasteless  powder,  in- 
soluble in  water  but  completely  soluble  in  dilute  nitric  acid,  with 
effervescence. 

BISMUTH    SUBGALLATE. 

BISMUTHI    SUBGALLAS. 

Crystallized  normal  bismuth  nitrate 100  Gm 

Glacial  acetic  acid 200  Gm 

Gallic  acid 33  Gm 

Dissolve  the  bismuth  nitrate  in  the  acetic  acid  and  dilute  the 
solution  with  500  Gm  of  distilled  water.  Filter.  Add  gradually 
to  this  liquid  a  solution  of  the  gallic  acid  in  1,500  Gm  of  cold  dis- 
tilled water.  Wash  the  precipitate  with  tepid  distilled  water 
until  the  washings  are  free  from  nitric  acid.  Dry  the  product 
at  from  70°  to  80°  C.  on  blotting  paper  spread  upon  porous  tiles. 

Description. — A  sulphur  yellow,  odorless  and  tasteless  powder ; 
insoluble  in  water  or  in  alcohol.  Probably  practically  identical 
with  the  preparation  called  "dermatol." 

BISMUTHYL    NITRATE. 

BISMUTHI    SUBNITRAS. 

Chiefly  OBiNO8.H2O= 304. 

Bismuth,  in  small  pieces -. .  500  Gm 

Nitric  acid 1,500  ml 

Sodium   carbonate 2,500  Gm 

Ammonia  water 1,250  ml 

Distilled  water,  sufficient. 

Mix  800  ml  of  the  nitric  acid  with  1,000  ml  of  the  distilled 
water  in  a  capacious  glass  vessel,  add  the  bismuth,  and  set  aside 
for  twenty-four  hours  to  dissolve.  Dilute  the  solution  with 
2,500  ml  of  distilled  water,  so  that  the  turbidity  produced  by  the 
addition  of  the  water  no  longer  disappears  on  stirring;  stir  well, 
and  again  set  it  aside  for  twenty-four  hours.  Then  filter. 


BISMUTH    SUBNITRATE.  309 

Dissolve  the  sodium  carbonate  in  5,000  ml  of  distilled  water, 
with  the  aid  of  heat,  filter  the  solution,  and  let  it  rest  until  cold. 
Then  add  the  cold  solution  of  bismuth  nitrate  very  slowly,  and 
with  constant,  active  stirring,  to  the  sodium  carbonate  solution. 
Transfer  the  whole  to  a  wetted  muslin  strainer,  let  drain,  wash 
with  distilled  water  until  the  washings  pass  tasteless,  and  then 
let  it  drain  again  as  completely  as  possible. 

Put  the  moist  precipitate  in  a  suitable  vessel,  gradually  add 
the  remainder  of  the  nitric  acid,  being  careful  to  avoid  foaming 
over,  and  when  all  has  dissolved,  also  add  gradually  1,000  ml 
of  distilled  water,  and  set  the  solution  aside  for  twenty-four  hours. 
Then  filter. 

Dilute  the  filtrate  by  adding  gradually  6,000  ml  of  distilled 
water,  stirring  well.  Then  add  to  this,  very  slowly,  the  ammonia 
water,  through  a  small  siphon,  stirring  constantly.  Transfer 
the  whole  at  once  to  a  strainer,  and  after  draining  rapidly,  pour 
over  the  precipitate  8,000  ml  of  distilled  water,  let  it  drain  again, 
and  press  out  as  much  of  the  liquid  as  possible. 

Then  dry  the  product  on  bibulous  paper  with  a  gentle  heat, 
and  rub  it  "into  powder. 

Reaction.  First  the  bismuth  is  dissolved  in  the  nitric  acid  to 
form  normal  bismuth  nitrate,  thus: 


3^2Bi  (  NO3  )  3+N2O2+4H2O. 
Then  bismuth  subcarbonate  is  made  : 

2Bi(N03)3+3Na2C03.H20 

=(BiO)2CO3.H2O+6NaNO3+2CO2. 

The  bismuth  subcarbonate  is  next  re-dissolved  in  nitric  acid  to 
form  normal  bismuthous  nitrate  again  : 

(  BiO)  2CO3.H2O.+6HNO3=2Bi  (  NO3)  3-f  4H2O+CO2. 

Finally  the  normal  bismuthous  nitrate  is  converted  into  subnitrate 
as  follows: 

Bi(NO3)3+2H3N+2H2O=OBiNO3.H2O+2H4NNO3. 

Notes.     The  metal  dissolves  rapidly  at  first,  but  toward  the  last 
it  is  best  to  apply  heat  if  economy  of  time  is  desired.     Perforated 


3IO  BISMUTH    SUBNITRATE. 

baskets  of  stoneware  are  used  for  suspending  the  bismuth  in  the 
acid  when  bismuth  preparations  are  prepared  on  a  moderately 
large  scale,  the  acid  being  placed  in  a  stone  pot  and  the  basket 
containing  the  bismuth  suspended  just  below  the  surface  of  the 
acid.  Unless  the  vessel  in  which  the  solution  is  effected  is  suf- 
ficiently large  to  obviate  all  risk  and  inconvenience  from  the  viol- 
ence of  the  reaction,  the  metal  should  be  added  in  portions,  each 
portion  to  be  entirely  dissolved  before  more  is  added.  The  ca- 
pacity of  the  vessel  ought  to  be  about  three  times  the  combined 
volume  -of  the  acid  and  water  used  to  dissolve  the  metal. 

The  strong  solution  can  not  be  filtered  through  paper,  for  the 
acid  liquid  is  so  corrosive  as  to  destroy  the  paper,  not  only  de- 
feating the  filtration  but  also  discoloring  the  solution.  It  is  best 
to  filter  through  coarsely  powdered  glass  or  glass  wool,  or 
washed  asbestos;  sometimes  the  solution  is  filtered  through  cot- 
ton previously  immersed  in  dilute  nitric  acid.  Decantation  is  the 
easiest  method,  and  generally  sufficient,  especially  when  large 
quantities  are  operated  upon.  After  dilution,  however,  filtration 
through  paper  is  entirely  practicable. 

The  object  of  first  preparing  subcarbonate  of  bismuth  is  to  get 
rid  of  the  arsenic  which  the  metal  contained.  This  arsenic  is 
held  in  the  acid  solution  as  bismuth  arsenate,  nearly  all  of  which 
precipitates  upon  dilution  of  the  liquid  with  water,  and  is  re- 
moved by  filtration  after  standing  twenty-four  hours.  The  re- 
mainder of  the  arsenic  is  left  in  the  last  mother-liquor  as  am- 
monium arsenate,  together  with  the  ammonium  nitrate  after  pre- 
cipitation of  the  bismuth  subnitrate  with  ammonia. 

The  character  and  composition  of  subnitrate  of  bismuth  de- 
pend greatly  upon  the  method  of  its  preparation.  Among  the 
most  important  influences  that  affect  the  character  of  the  product 
are  these :  The  relative  quantity  of  water  used  in  the  precipita- 
tion ;  the  length  of  time  the  precipitate  is  exposed  to  the  mother- 
liquor;  the  amount  and  temperature  of  the  water  used  for  the 
precipitation ;  the  quantity  of  water  and  the  length  of  time  con- 
sumed in  washing ;  the  use  or  omission  of  ammonia ;  and  the 
greater  or  less  care  bestown  upon  the  various  details  of  the 
process. 

The  process  given  above  probably  yields  the  most  uniform  and 
satisfactory  results.  In  order  to  insure  success  each  step  of  the 


BISMUTH    SUBNITRATE.  31 1 

process  should  be  carried  out  in  strict  accordance  with  the  precise 
directions  given. 

Other  processes  prescribe  that  the  solution  of  bismuthous  nit- 
rate be  evaporated  to  crystallization  and  the  crystals  afterward 
treated  with  a  definite  quantity  o'f  water.  The  evaporation  must 
not  be  carried  so  far  that  a  cake  forms  on  the  bottom  of  the  dish, 
for  then  the  salt  will  be  hard  and  difficult  to  manage.  The  clear 
crystals  removed  from  the  mother  liquor  are  carefully  made  dry 
by  gently  pressing  them  between  blotting  paper,  which  operation 
must  be  very  carefully  carried  out  so  as  not  to  soil  the  crystals 
with  fibers  from  the  paper.  No  heat  must  be  used  in  drying  the 
crystals.  Triturate  one  part  of  the  crystallized  salt  very  thor- 
oughly with  four  parts  of  distilled  water,  and  then  pour  this 
mixture  into  a  large  vessel  containing  twenty-one  parts  of  boil- 
ing distilled  water,  stirring  constantly.  Let  cool ;  decant ;  and 
wash  the  precipitate  on  a  strainer  with  ten  parts  of  cold  distilled 
water,  gradually  added.  After  draining  as  rapidly  as  possible, 
press  out  the  last  of  the  wasrpwater  by  means  of  a  screw  press, 
and  dry  the  product  on  filter  paper  at  not  over  30°  C. 

In  order  to  obtain  a  good  product,  the  nitric  acid  used  must  be 
pure,  distilled  water  must  be  used,  and  the  acid  solutions  must 
not  come  in  contact  with  wood  or  other  organic  substances,  or 
with  metals. 

Whenever  the  precipitated  bismuth  subnitrate  is  permitted  to 
remain  long  in  contact  with  the  mother  liquor  in  which  it  has  been 
thrown  down,  it  becomes  more  dense,  and  at  the  same  time  takes 
up  more  nitric  acid.  This  must  be  avoided.  Long  contact  with 
much  water  also  renders  the  preparation  heavier,  but  at  the  same 
time  more  basic.  Cold  liquids  will  yield  a  voluminous  precipi- 
tate; hot  water  makes  the  precipitate  more  dense.  If  the  water 
used  for  precipitating  is  50°  C.  the  precipitated  subnitrate  will 
have  a  composition  corresponding  to  about  77  per  cent  of  Bi2O3 ; 
if  the  water  is  boiling  hot  (100°  C.)  the  subnitrate  will  have  a 
composition  corresponding  to  about  80  to  81  per  cent  of  Bi,O3. 
According  to  Loewe,  the  precipitate  is  not  affected  by  a  solution 
of  ammonium  nitrate,  and  hence  it  can  be  washed  with  such  a 
solution  without  danger. 

The  precipitate  must  be  dried  at  a  low  temperature  (not  over 
30°  C.),  but  must  be  thoroughly  dry  before  -it  is  put  away. 
After  removing  all  water  that  can  be  gotten  rid  of  by  pressing 


312  BISMUTHYL    CHLORIDE. 

it,  the  precipitate  should  be  dried  in  layers.  If  not  thoroughly 
dried  it  decomposes  by  the  influence  of  light  and  acquires  a  nitrous 
odor.  If  dried  properly  in  layers,  these  can  be  easily  broken  and 
powdered  by  rubbing  the  pieces  through  a  fine  wire  sieve  by 
means  of  a  soft  brush.  If  dried  at  too  high  a  temperature  the 
pieces  are  hard,  not  so  readily  powdered,  and  apt  to  yield  a  coarse, 
harsh  powder. 

Good  subnitrate  of  bismuth  is  soft  and  bulky. 

Description. — A  fine,  white  powder,  odorless,  almoct  tasteless; 
insoluble  in  water,  alcohol,  and  glycerin. 

Bismuth  subnitrate  is  always  a  comparatively  heavy  substance, 
but  it  must  be  as  bulky  as  it  can  be  made.  The  product  varies 
extremely  in  this  particular.  A  relatively  very  heavy  and  coarse 
preparation  is  not  fit  for  medicinal  uses. 


BISMUTHYL    CHLORIDE. 

BISMUTHI  OXYCHLORIDUM. 

(Oxychloride  of  Bismuth.) 
OBiCl= 259.4. 

Bismuth 14  Gm 

Nitric  acid    23  ml 

Sodium  chloride 39  Gm 

Distilled  water,  sufficient. 

Mix  the  acid  with  30  ml  of  water ;  dissolve  the  metal  in  the 
mixture.  Dissolve  the  sodium  chloride  in  400  ml  of  distilled  water, 
and  filter.  Pour  the  acid  solution  of  bismuth  nitrate  gradually 
and  with  constant  stirring  into  the  solution  of  sodium  chloride. 

Wash  the  precipitate  with  distilled  water,  first  by  decantation 
and  afterwards  on  a  filter,  until  the  washings  are  tasteless.  Drain, 
and  then  dry  the  product  between  bibulous  paper  with  the  aid 
of  gentle  heat. 

Reaction.     OBiNO3+NaCl=NaNO,+OBiCl. 
Description. — A  fine,  white,  odorless  and  tasteless  powder. 


BISMUTHYL    IODIDE.  313 

BISMUTHYL  IODIDE. 

BISMUTHI    OXIODIDUM. 

(Oxy-iodide  of  Bismuth.) 


Bismuth  subnitrate  ..................     12  parts 

Potassium  iodide  ....................       7  parts 

Distilled  water  ...................  ...      15  parts 

Mix  and  digest  together  in  a  bottle  for  an  hour,  shaking  occa- 
sionally. Then  transfer  to  a  filter,  and  wash  with  warm  water 
until  the  washings  are  tasteless.  Drain,  and  dry  between  filter- 
paper. 

Reaction.     BiONO8.H2O+KI=KNO8+BiOI+H2O. 
O.  Kaspar's  Method. 

Crystallized  normal  bismuth  nitrate  .....   94.5  Gm 

Distilled  water  .......................   30      liters 

Nitric  acid,  the  least  quantity  sufficient. 

to  dissolve  the  bismuth  nitrate  in  the 

water. 

Make  a  solution  : 

Potassium  iodide  ...............  ......  33.2  Gm 

Distilled   water    ......................     3      liters 

Dissolve. 

Mix  the  two  solutions. 

When  the  brown  precipitate  has  changed  to  yellowish  and 
finally  to  brick-red,  wash  it  by  decantation  and  afterward  on  a 
filter,  and  dry  it  at  about  100°  C. 

B.  Fischer's  Method. 

Crystallized  normal  bismuth  nitrate.  .  .  .  95.4  Gm 

Glacial  acetic  acid   ..................  120      ml 

Potassium   iodide    ...  ................  33.2  Gm 

Sodium  acetate   .  .  .  ..................  50      Gm 

Distilled  water,  sufficient. 


314  BISMUTH    TANNATE. 

Dissolve  the  bismuth  nitrate  in  the  glacial  acetic  acid.  Dissolve 
the  potassium  iodide  and  the  sodium  acetate  in  2  liters  of  distilled 
water.  Mix  the  clear  solutions,  constantly  stirring,  pouring  the 
bismuth  solution  gradually  into  the  other. 

A  yellowish-brown  precipitate  is  formed,  which  changes  to 
lemon-yellow,  and  finally  to  brick-red.  Wash  the  precipitate  by 
decantation  and  dry  it  at  100°  C. 

Should  be  kept  protected  from  light. 

Description. — A  brick-red,  micro-crystalline  powder,  odorless, 
tasteless,  insoluble  in  water  and  in  alcohol. 

On  ignition  it  should  yield  not  less  than  66  per  cent  of  Bi2O3. 

BISMUTH  TANNATE. 

BISMUTHI    TANNAS. 

Normal  bismuthous  nitrate 60  Gm 

Glycerin 200  ml 

Tannic  acid 27  Gm 

Solution  of  soda,  240  ml,  or  sufficient. 

Triturate  the  bismuth  nitrate  to  powder ;  add  the  glycerin  and 
stir  until  dissolved ;  then  gradually  add  solution  of  soda  until  a 
precipitate  no  longer  forms,  stirring  well;  wash  the  precipitate 
with  distilled  water  until  the  washings  are  tasteless;  drain;  add 
the  tannic  acid  to  the  moist  hydroxide,  mix  well,  and  set  aside  for 
two  hours,  stirring  frequently.  Then  transfer  the  mixture  to  a 
filter,  wash  with  distilled  water  until  the  washings  are  tasteless, 
and  dry  the  product. 

Description. — A  dirty-white  or  pale  yellowish,  odorless  and 
tasteless  powder. 

BROMINE. 

BROMUM. 

Br2=i6o. 

Bromine  is  a  heavy,  dark-red,  fuming  liquid  of  a  peculiar,  suf- 
focating odor  and  its  vapor  is  terribly  irritating  and  dangerous  to 
the  eyes  and  respiratory  organs. 


CADMIUM    CARBONATE.  315 

Commercial  bromine  usually  contains  some  chlorine  and  iodine. 
It  must  be  kept  in  small  glass-stoppered  bottles  in  a  cool  place. 
See  also  Part  II,  Vol.  I,  and  Part  I  of  this  volume. 

Solutions  of  Bromine. 

Water  solutions  of  bromine  are  frequently  required  for  surgical 
and  other  uses.  They  may  be  prepared  with  the  aid  of  potassium 
bromide.  One  such  solution,  which  is  commonly  employed,  con- 
tains 10  Gm  of  bromine  and  20  Gm  of  potassium  bromide  dis- 
solved in  one  liter  of  distilled  water  ;  another  contains  20  Gm  of 
bromine,  10  Gm  of  potassium  bromide  and  800  ml  of  distilled 
water.  But  as  bromine  is  soluble  in  30  parts  of  water  at  15°,  a 
simple  water-solution  containing  any  quantity  of  bromine  below 
three  per  cent  may  be  readily  made  as  required. 

CADMIUM  CARBONATE. 

CADMII   CARBON  AS. 


Cadmium    ............................  10  parts 

Nitric  acid   (68%   of  HNO3)  ..........  28  parts 

Ammonium  carbonate  .................  15  parts 

Water. 

Granulate  the  cadmium  by  pouring  the  fused  metal  from  a 
height  of  about  four  feet  into  a  vessel  of  water.  Add  the  granu- 
lated metal  gradually  to  the  nitric  acid  previously  diluted  with 
about  one-half  its  volume  of  water.  When  all  of  the  cadmium  has 
been  added  and  the  reaction  has  subsided,  set  the  solution  (with 
the  undissolved  residue  of  metal)  on  a  water-bath  and  heat  until 
effervescence  has  entirely  ceased.  Dilute  the  solution  with  about 
30  parts  of  water.  Let  the  whole  stand  at  rest  for  a  few  hours. 
Filter.  Put  the  filtrate  in  a  large  vessel  and  add  400  parts  of  hot 
water. 

Dissolve  the  ammonium  carbonate  in  150  parts  of  water.  Add 
a  small  portion  of  this  solution  gradually  to  the  solution  of  cad- 
mium nitrate  to  precipitate  iron  from  it.  When  a  test  portion  of 
the  cadmium  nitrate  solution  shows  no  further  test  for  iron,  filter 


316  CADMIUM   CHLORIDE. 

the  liquid  and  pour  it  into  the  remainder  of  the  solution  of  am- 
monium carbonate.  Wash  the  precipitated  cadmium  carbonate 
by  decantation  until  free  from  nitrate  and  ammonium  salt,  collect 
it,  and  dry  it. 

Enactions.     3Cd+8HNO8=3Cd  ( NO3 )  2+4H2O+2NO. 
then,  Cd(N03)2+(H4N)2C03=CdC03+(H4N)2N03. 

Description. — An  insoluble,  amorphous,  odorless  and  tasteless, 
white  powder. 

CADMIUM  CHLORIDE. 

CADMII  CHLORIDUM. 
CdCl2.2H2O=2l8.8. 

Saturate  hydrochloric  acid  with  cadmium  carbonate,  digest  the 
solution  with  a  slight  excess  of  the  carbonate,  filter,  and  evap- 
orate to  dryness.  Dissolve  the  dry  salt  in  two-thirds  of  its  own 
weight  of  hot  distilled  water,  acidulate  with  hydrochloric  acid, 
and  set  the  liquid  aside  for  several  hours  to  crystallize.  Dry  the 
crystals  with  the  aid  of  moderate  heat,  or  in  a  desiccator  over 
sulphuric  acid. 

Description. — Colorless  crystals,  readily  soluble  in  water  and  in 
alcohol. 

* 

CADMIUM    IODIDE. 

CADMII     IODIDUM. 

CdI2=36S. 

Granulated  cadmium    15  parts 

Iodine    33  parts 

Distilled  water 100  parts 

Put  the  metal,  iodine  and  water  into  a  flask  and  place  this  in 
warm  water,  or  keep  its  contents  at  about  80°,  until  the  odor  of 
iodine  has  passed  and  the  metal  is  nearly  all  dissolved.  Then 
heat  to  boiling  for  a  few  minutes,  filter  hot,  evaporate  to  satura- 
tion, and  set  aside  to  cool  and  crystallize.  Drain  the  crystals  and 


CADMIUM    NITRATE.  317 

dry  them  between  blotting  paper,  or  over  sulphuric  acid.    Evap- 
orate the  mother-liquor  to  recover  more  crystals. 

Reaction.     Cd+I2=CdI2. 

Description, — Beautiful,  thin,    pearly,    white    plates,  odorless, 
readily  water-soluble.    Also  soluble  in  alcohol  and  in  ether. 


CADMIUM   NITRATE. 

CADMII    NITRAS. 

Cd(N03)2.4H20=3o8. 

Dissolve  granulated  cadmium  in  dilute  nitric  acid  to  saturation, 
acidulate  the  solution,  and  evaporate  to  crystallization. 

Description. — Colorless,  deliquescent,  needle-like  crystals. 
CADMIUM  SULPHATE. 

CADMII    SULPHAS. 

3CdSO4.8H2O=976. 

Saturate  moderately  diluted  sulphuric  acid  with  cadmium  hy- 
droxide, acidulate  the  solution  with  some  more  of  the  acid,  filter, 
and  evaporate  to  crystallization. 

Notes.  The  salt  may  also  be  made  by  dissolving  granulated 
cadmium  in  sulphuric  acid  of  about  twenty  per  cent  strength ;  but 
the  metal  dissolves  very  slowly. 

Description. — Large  colorless  crystals,  very  readily  water-sol- 
uble, the  solution  having  an  acid  reaction. 

CALCIUM   ACETATE. 

CALCII  ACETAS. 

Ca(C2H3O2)2.2H2O=i94. 

Calcium  carbonate 3  parts 

Acetic  acid  (36%  of  HC2H3O2) 10  parts 

Water    2  parts 


318  CALCIUM    BENZOATES. 

Mix  in  a  large  porcelain  dish  and  dissolve  with  the  aid  of  mod- 
erate heat.  Filter,  and  evaporate  to  crystallization. 

Description. — White,  crystalline,  readily  soluble  in  water.  Ef- 
florescent. Odorless ;  taste  saline,  bitterish. 

CALCIUM  BENZOATE. 

CALCII  BENZOAS. 

Ca(C7H502)24H20=354. 

Lime i  part 

Benzoic  acid 4  parts 

Water    1 50  parts 

Slake  the  lime  in  a  porcelain  dish  with  a  part  of  the  water. 
When  the  reaction  has  been  completed  add  the  remainder  of  the 
water,  mix  thoroughly,  and  then  add  the  benzoic  acid.  Boil  the 
mixture  a  few  minutes  until  the  benzoic  acid  is  dissolved.  Filter 
the  solution  while  hot.  Evaporate  the  filtrate  to  one-half  its  vol- 
ume and  set  it  aside  to  cool.  Collect  the  crystals  and  drain  and 
dry  them.  Recover  the  remainder  of  the  salt  from  the  mother- 
liquor  by  evaporation  in  the  usual  way. 

Notes.  Very  large,  long  crystals  can  be  obtained  by  spon- 
taneous evaporation  of  a  saturated  solution.  The  crystals  may 
be  dried  with  'the  aid  of  gentle  heat.  When  the  mother-liquor 
ceases  to  yield  enough  to  warrant  further  evaporation,  the  benzoic 
acid  may  be  recovered  from  it  by  precipitation  with  a  sufficient 
amount  of  hydrochloric  acid. 

Description. — Long,  white  needles,  soluble  in  about  25  parts  of 
water  at  15°,  and  in  a  smaller  proportion  of  boiling  water. 

CALCIUM   BROMIDE. 

CALCII  BROMIDUM. 

CaBr2=200. 

Ammonium  bromide 3  parts 

Lime    i  part 

Slake  the  lime  with  6  parts  of  water  and  triturate  it  in  a  mortar, 
adding  enough  water  to  form  a  liquid  mixture.  Dissolve  the  am- 


CALCIUM    CARBONATE.  319 

monium  bromide  in  8  parts  of  water,  heat  to  the  boiling  point, 
and  then  add  the  milk  of  lime  until  the  evolution  of  ammonia 
ceases.  Then  filter  the  solution  and  evaporate  the  filtrate  to  dry- 
ness,  stirring  constantly  so  as  to  produce  a  granulated  salt. 

Reaction.     2H4NBr+CaO==CaBr2-f-H2O+2H3N. 

Description. — A  white,  granular  salt ;  odorless ;  taste  sharp, 
saline.  Deliquescent.  Soluble  at  15°  in  0.7  part  of  water  and  in 
i  part  of  alcohol ;  extremely  readily  soluble  in  boiling  water  or 
alcohol.  The  solution  is  neutral  to  test-paper. 


CALCIUM  CARBONATE;  PRECIPITATED. 

CALCII     CARBONAS     PRAECIPITATUS. 

CaCO3=ioo. 

Calcium  chloride,  fused 10  parts 

Sodium  carbonate   26  parts 

Distilled  water,  sufficient. 

Dissolve  the  calcium  chloride  in  100  parts  of  the  water,  and  the 
sodium  carbonate  in  another  equal  quantity.  Filter  the  solutions. 
Heat  both  solutions  to  about  80°  C.  Pour  the  solution  of  calcium 
chloride  into  the  solution  of  sodium  carbonate,  stirring  constantly. 
Wash  the  precipitate  by  decantation;  then  collect  and  dry  it. 

Reaction.    CaCl2+Na2CO8=CaCO8+2NaCl. 

Notes.  Hot  solutions  are  used  to  insure  a  dense  precipitate,  so 
that  the  process  of  washing  may  be  easier ;  when  cold  solutions  are 
used  the  precipitated  calcium  carbonate  is  a  very  bulky  magma, 
difficult  to  wash  free  from  sodium  chloride. 

The  precipitate  should  be  washed  until  the  washings  cease  to  be 
rendered  turbid  by  test  solution  of  silver  nitrate,  and  then  dried 
at  100°  C. 

Another  Method. 

Prepare  a  solution  of  calcium  chloride  from  white  marble,  as 
described  under  the  title  of  Calcium  Chloride,  removing  iron, 
aluminum  and  magnesium  by  employing  chlorine  water  and  milk 
of  lime.  Render  the  solution  alkaline  by  using  a  sufficiency  of 


32O  CALCIUM    CARBONATE. 

milk  of  lime.  Filter.  Then  acidulate  the  liquid  with  hydrochloric 
acid.  Precipitate  this  solution  with  either  ammonium  carbonate 
or  sodium  carbonate. 

Description, — A  very  fine,  perfectly  white  powder,  odorless, 
tasteless,  and  insoluble  in  water  and  in  alcohol.  Under  the  micro- 
scope the  precipitated  calcium  carbonate  is  seen  to  be  micro-crys- 
talline. 

Prepared  Chalk. 

Triturate  1000  Gm  of  chalk  with  a  little  water  until  reduced  to 
a  very  fine  powder  by  the  "levigation."  Throw  the  mixture  into 
a  vessel  capable  of  holding  about  twenty  liters  and  nearly  filled 
with  water,  stir  the  mixture  well,  and,  after  a  brief  time,  decant 
the  supernatant  liquid,  while  yet  white  and  turbid  from  the  sus- 
pended particles  of  the  finely  divided  chalk,  into  another  vessel. 
To  the  residue  in  the  first  vessel  add  a  fresh  portion  of  water,  stir 
well  again,  and  after  allowing  the  coarser  particles  to  subside  as 
before,  decant  once  more,  adding  the  second  turbid  liquid  to  that 
previously  decanted.  Set  the  mixed  liquors  aside,  and  when  the 
fine  powder  has  subsided  perfectly,  pour  off  the  water,  and  collect 
and  dry  the  powder. 

Note.  This  process  of  separating  the  coarse,  gritty  particles 
from  the  levigated  chalk  is  called  "elutriation,"  the  object  bein^ 
to  obtain  a  very  soft,  finely  divided  product. 

Instead  of  drying  the  product  as  a  mass,  the  moist  powder  may 
be  formed  into  cones  by  "trochiscation." 

Description. — A  light,  amorphous,  cream-colored,  nearly  white, 
very  soft  powder,  or  conical  lumps ;  odorless  and  tasteless.  Insol- 
uble in  water  and  in  alcohol. 

CALCIUM  CHLORIDE. 

CALCII    CHLORIDUM 

CaCl3=no.8. 

White  marble,  in  powder 250  Gm 

Hydrochloric  acid  (31.9%  of  HC1) 500  ml 

Water 500  ml 

Chlorine  water. 
Lime. 


CALCIUM    CHLORIDE.  321 

Mix  the  acid  and  water.  Add  the  marble  in  small  portions, 
stirring  well,  and  let  the  effervescence  subside  after  each  addi- 
tion before  adding  more.  When  all  the  marble  has  been  added 
and  the  reaction  has  nearly  ceased,  heat  the  mixture  to  boiling 
until  no  more  marble  dissolves,  replacing  the  water  lost  by  evap- 
oration. Add  to  the  hot  liquid  15  ml  of  strong  chlorine  water, 
stir  well,  and  continue  boiling  for  half  an  hour.  Add  milk  of 
lime  a  sufficient  quantity  to  render  the  liquid  distinctly  alkaline. 
Filter  while  hot.  Evaporate  to  dryness  in  a  tared  dish  and  fuse 
the  residue  at  a  low  red  heat. 

Keep  the  product  in  tightly  closed  bottles. 

Reaction.     CaCO8+2HCl=CaCl2+H2O+CO2. 

Notes.  Marble  is  liable  to  contain  some  iron.  Used  in  excess 
it  reprecipitates  dissolved  iron  and  other  metals.  The  chlorine 
water  has  for  its  object  the  oxidation  of  the  iron  to  the  ferric  con- 
dition to  facilitate  precipitation,  which  is  further  insured  by  the 
addition  of  milk  of  lime. 

Should  the  product  still  contain  iron  after  fusion,  it  must  be 
redissolved  in  twice  its  weight  of  boiling  water,  again  treated  with 
chlorine  water,  and  also  with  either  milk  of  lime  or  pure  calcium 
carbonate,  the  hot  solution  filtered,  and  again  evaporated  to  dry- 
ness  and  the  residue  fused.  In  evaporating  to  dryness  add  hydro- 
chloric acid  occasionally  to  prevent  the  product  from  becoming 
alkaline. 

Description. — Hard  white  pieces  or  masses ;  odorless ;  taste 
saline,  acrid.  Highly  deliquescent.  Soluble  in  1.5  parts  of  water 
at  15°  and  in  8  parts  of  alcohol;  in  1.5  parts  of  boiling  alcohol 
and  freely  in  boiling  water. 

CALCIUM   HYDROXIDE. 

CALCII     HYDROXIDUM. 

Ca(OH)2=74. 

Lime    8  parts 

Water 5  parts 

Place  the  lime  in  a  metal  pot,  pour  the  water  upon  it,  and  when 

Vol.    11—21 


322  CALCIUM    HYDROXIDE. 

vapor  ceases  to  be  disengaged,  cover  the  pot  well  and  set  it  aside 
until  the  contents  are  cool.  Put  the  slaked  lime  into  an  iron-wire 
sieve,  and  by  gently  shaking  cause  the  fine  powder  to  pass  through 
the  sieve,  rejecting  what  is  left.  Put  the  powder  into  a  bottle  and 
cork  tightly. 

Notes.  Only  recently  prepared  calcium  hydroxide  is  fit  to  be 
used  for  any  of  the  purposes  for  which  slaked  lime  is  prescribed, 
as  it  soon  becomes  contaminated  with  carbonate.  It  should  be 
perfectly  white. 

The  water  should  be  added  to  the  lime  all  at  once ;  otherwise, 
when  too  little  water  is  added  at  first,  the  hydrate  formed  will  be 
coarse  and  hard,  and  does  not  afterward  disintegrate  readily  on 
addition  of  more  water. 

Good,  clean,  white  calcium  oxide  must  be  used  to  obtain  a  suffi- 
ciently pure  and  white  hydroxide. 

Calcium  Hydroxide  Solution. 
(LIQUOR  CALCIS.    LIME  WATER.) 

A  saturated  aqueous  solution  of  calcium  hydroxide  contains 
about  0.17  per  cent  of  that  compound. 

Lime i  part 

Distilled  water 300  parts 

Water,  sufficient. 

Slake  the  lime  by  the  gradual  addition  of  6  parts  of  water,  then 
add  300  parts  of  water  and  stir  occasionally  during  half  an  hour. 
Allow  the  mixture  to  settle,  decant  the  liquid  and  throw  this  away. 
Now  add  to  the  residue  300  parts  of  distilled  water,  stir  well,  wait 
a  short  time  for  the  coarser  particles  to  subside,  and  pour  the 
liquid,  holding  the  undissolved  lime  in  suspension,  into  a  glass- 
stoppered  bottle.  Pour  off  the  clear  liquid  when  wanted  for  use. 

Notes.  The  object  of  rejecting  the  solution  first  made  is  to  re- 
move dust  and  alkalies.  After  this  washing  the  calcium  hydroxide 
furnishes  a  purer  product. 

At  19°. 5  C.  water  dissolves  about  ^  of  its  weight  of  cal- 
cium hydroxide. 

When  a  solution  of  calcium  hydroxide  is  exposed  to  the  air, 


CALCIUM    HYPOPHOSPHITE.  323 

which  happens  each  time  the  stopper  is' removed  from  the  con- 
tainer, some  CO2  from  the  air  precipitates  calcium  carbonate  from 
the  liquid,  thereby  reducing  the  quantity  of  Ca(OH)2  in  solution. 
But  if  an  excess  of  the  hydroxide  is  allowed  to  remain  in  the  stock 
bottle,  the  solution  is  kept  saturated. 

Syrup  of  Lime. 

Lime 65  Gm 

Sugar 400  Gm 

Water. 

Triturate  the  lime  and  sugar  thoroughly  in  a  mortar,  so  as  to 
form  a  homogeneous  powder ;  then  add  the  mixture  to  500  ml  of 
boiling  water,  contained  in  a  bright  copper  or  tinned  iron  vessel, 
boil  for  five  minutes,  constantly  stirring,  and  then  strain.  Dilute 
the  strained  liquid  with  an  equal  volume  of  water,  and  filter 
through  white  paper.  Then  evaporate  the  filtrate,  in  a  tared  cap- 
sule, to  700  Gm,  allow  it  to  cool,  add  to  it  enough  water  to  make 
the  product  measure  1000  ml,  and  mix  thoroughly. 

Keep  the  syrup  in  well-stoppered  bottles. 

Notes.  The  preparation  contains  a  chemical  compound  formed 
by  the  lime  with  the  sugar,  called  calcium  sucrate,  which  may, 
however,  dissolve  more  lime.  It  is  best  to  dissolve  the  sugar  in 
the  water,  heat  to  boiling,  and  then  add  recently  prepared  calcium 
hydroxide  in  powder.  The  calcium  hydroxide  may  be  prepared 
by  slaking  65  Gm  of  calcium  oxide  with  40  Gm  of  water.  The 
calcium  hydroxide  may  also  be  dissolved  without  heat. 

Description. — A  clear,  colorless  syrup,  of  alkaline  taste. 
CALCIUM    HYPOPHOSPHITE. 

CALCII  HYPOPHOSPHIS. 

Ca(P02H2)2=i7o. 

Phosphorus I  part 

Lime 2  parts 

Distilled  water. 
Carbon  dioxide. 

Put  the  phosphorus  in  a  bottle  containing  20  parts  of  a  saturated 
solution  of  sodium  chloride  and  large  enough  to  be  only  about 


324  CALCIUM    HYPOPHOSPHITE. 

half  filled  by  these  contents.  Heat  the  bottle  gradually  by  plac- 
ing it  in  a  vessel  of  hot  water  (about  50°)  until  the  phosphorus 
becomes  liquid.  Shake  the  bottle  until  cold.  Wash  the  granu- 
lated phosphorus  two  or  three  times  with  distilled  water. 

Place  the  lime  in  a  porcelain  dish  and  add  20  parts  of  water. 
When  the  lime  has  been  completely  converted  into  calcium  hy- 
droxide and  intimately  mixed  with  the  water  to  form  a  creamy 
mixture,  add  the  granulated  phosphorus  and  stir  well.  Heat  the 
mixture  at  about  40°,  stirring  frequently,  until  the  phosphorus 
is  all  dissolved,  which  may  be  known  by  the  fact  that  the  evolution 
of  phosphine  ceases. 

Now  add  enough  distilled  water  to  make  the  liquid  measure 
about  40  parts,  filter  it,  and  conduct  into  the  filtrate  a  current  of 
carbon  dioxide  as  long  as  any  precipitate  continues  to  be  formed, 
keeping  the  liquid  at  about  60°  during  this  part  of  the  process. 
Filter  out  the  calcium  carbonate. 

Evaporate  the  filtrate  over  a  water-bath  to  dryness,  being  care- 
ful not  to  permit  the  temperature  to  exceed  60°.  Redissolve  the 
dry  salt  in  six  times  its  weight  of  hot  distilled  water  (not  over 
60°),  filter  again  (if  necessary  to  make  the  solution  perfectly 
clear),  and  evaporate  it  at  40°  in  a  porcelain  dish  to  about  one- 
half  its  volume.  Let  it  cool.  Collect  the  crystalline  salt  which 
has  been  formed,  drain  it  well,  and  dry  it  with  the  aid  of  gentle 
heat. 

Evaporate  the  mother-liquor  to  one-half  its  volume,  let  it  cool, 
and  collect  and  dry  the  second  crop  of  crystalline  salt  in  the  same 
manner  as  the  first.  Evaporate  the  second  mother  liquor  in  the 
same  way. 

Reaction.     3Ca  ( OH )  2+8P+6H2O=3Ca  ( PO2H2 )  2+2H3P. 

Notes.  When  phosphorus  is  digested  with  alkaline  hydroxides 
— whether  potassium,  sodium  or  calcium  hydroxide — the  products 
are  hypophosphites  and  hydrogen  phosphide.  The  reaction  is 
completed  when  no  more  phosphine  (hydrogen  phosphide)  is 
evolved.  This  gas  is  known  by  its  strong  garlic  odor.  Owing 
to  its  inflammable  nature  care  should  be  taken  that  no  accident 
may  happen.  To  guard  against  danger  from  a  too  rapid  evolution 
of  phosphine,  and  from  the  explosive  decomposition  of  the  hy- 
pophosphite,  the  temperature  must  be  kept  within  safe  limits,  as 
directed. 


CALCIUM    HYPOPHOSPHITE.  325 

The  lime  is  used  in  considerable  excess.  Hence  the  calcium 
hydroxide  which  is  contained  in  the  solution  with  the  hypophos- 
phite  must  be  decomposed  and  the  calcium  precipitated  as  carbon- 
ate by  conducting  carbon  dioxide  into  the  solution  and  by  heat- 
ing the  liquid  to  prevent  the  formation  of  soluble  calcium  bi- 
carbonate. 

The  solution  of  calcium  hypophosphite,  filtered  free  from  the 
precipitated  carbonate,  is  evaporated  to  dryness,  and  the  salt 
redissolved  in  a  definite  proportion  of  distilled  water.  A  beautiful 
product  can  then  be  obtained  from  the  filtered  solution  by  crys- 
tallization in  the  manner  described. 

But  in  order  to  obtain  a  perfect  product  it  is  necessary  that 
the  lime  used  shall  be  pure.  It  must,  therefore,  be  made  by  the 
calcination  of  a  pure  calcium  carbonate.  Distilled  water  must 
also  be  used  throughout  instead  of  common  natural  water. 

Description. — Colorless,  transparent  crystals,  or  pearly,  lustrous 
scales,  or  a  white  crystalline  powder;  odorless;  taste  bitter, 
nauseous.  Soluble  in  6.8  parts  of  water  at  15°,  and  in  a  somewhat 
smaller  quantity  of  boiling  water.  Insoluble  in  alcohol.  It  must 
be  neutral  to  litmus  paper.  . 

Syrup  of  Hypophosphites. 

Calcium  hypophosphite 45  Gm 

Potassium  hypophosphite 15  Gm 

Sodium  hypophosphite 15  Gm 

Diluted  hypophosphorous  acid 2  Gm 

Sugar 500  Gm 

Spirit  of  lemon 5     ml 

Water. 

Triturate  the  hypophosphites  with  450  ml  of  water  until  dis- 
solved, add  the  spirit  of  lemon  and  the  hypophosphorous  acid, 
and  filter  the  liquid.  In  the  filtrate  dissolve  the  sugar  by  agita- 
tion, without  heat,  and  add  enough  water,  through  the  filter, 
to  make  the  product  measure  1,000  ml.  Strain,  if  necessary. 

Syrup  of  Hypophosphites  with  Iron. 

Ferrous  lactate 10  Gm 

Potassium  citrate 10  Gm 

Syrup  of  hypophosphites. 


326  CALCIUM  IODIDE. 

Rub  the  ferrous  lactate  and  potassium  citrate  with  50  ml  of  hot 
distilled  water  until  dissolved.  Filter  the  solution.  Add  it  to 
1,000  ml  of  syrup  of  hypophosphites,  mix  well,  and  evaporate  to 
1,000  ml. 

This  preparation  should  be  freshly  made,  when  wanted. 

CALCIUM    IODIDE. 

CALCII  IODIDUM. 


Iodine  .....................  ..........  20  parts 

Iron   ......  .  ...............  ..........  8  parts 

Lime  ................................  5  parts 

Water,  sufficient. 

Digest  the  iron  and  15  parts  of  the  iodine  with  30  parts  of 
water,  in  a  flask,  until  all  odor  of  iodine  ceases  and  a  green 
solution  of  ferrous  iodide  is  obtained.  Filter  this,  then  add  the 
remainder  of  the  iodine,  and  dissolve. 

Slake  the  lime  with  6  parts  of  water,  and  triturate  the  cal- 
cium hydroxide  with  enough  water  to  make  a  smooth  liquid  mix- 
ture. Add  this  milk  of  lime  gradually  to  the  solution  of  iron 
iodides  until  the  iron  has  all  been  precipitated.  Then  filter  the 
liquid  and  evaporate  it  to  dryness,  stirring  constantly. 

Reactions. 

Fe+2l=  FeI2;  then  FeI2+I=FeI3;  then 

2FeI3+3Ca  (  OH)  2=3'CaI2+Fe2O8+H2O. 

Description.  —  A  white,  granular  salt;  odorless;  taste  acrid, 
saline,  reminding  of  iodine.  Deliquescent.  Readily  soluble  in 
water  and  in  alcohol. 

CALCIUM    LACTATE. 

CALCII  LACTAS. 

Ca(C3H503)2.5H20=3o8. 

Lactic  acid  (75%  )  ....................     30  parts 

Calcium  oxide  ...........  ............       7  parts 

Distilled  water  .......................   200  parts 


CALCIUM    OXIDE.  327 

Slake  the  calcium  oxide  with  about  50  parts  of  the  water ;  add 
the  remainder  of  the  water  to  the  lactic  acid.  Then  add  the  milk 
of  lime  gradually  to  the  diluted  lactic  acid  in  a  porcelain  dish 
heated  to  about  90°  C.  over  a  water-bath.  Filter  the  solution 
while  hot.  Separate  the  crystals  deposited  on  cooling,  and  dry 
them  between  blotting  paper.  Evaporate  the  mother-liquor  to 
obtain  more  crystals. 

Reaction.     2HC3H5O3+Ca  ( OH )  2=Ca  ( C3H5O3 )  2.2H2O. 

Notes.  The  mother-liquor  may  be  evaporated  to  dryness  to 
obtain  all  of  the  calcium  lactate ;  but  this  product  is  granular  and 
not  pure. 

Description. — Colorless,  inodorous  crystals,  soluble  in  9.5  parts 
of  water.  Freely  soluble  in  boiling  water.  Insoluble  in  alcohol. 


CALCIUM    OXIDE. 

CALCII  OXIDUM. 

(Calx.     Lime.) 


Fill  a  Hessian  crucible  with  pieces  of  white  marble,  or  with 
any  suitable  calcium  carbonate,  and  subject  it  to  a  red  heat  until 
completely  decomposed  so  that  the  residue  no  longer  effervesces 
on  being  mixed  with  dilute  hydrochloric  acid  after  having  been 
first  mixed  with  its  own  weight  of  water. 

Keep  the  product  in  tightly  closed  bottles  in  a  dry  place. 

Reaction.     CaCO3=CaO+CO2. 

Description.  —  Hard,  white  masses  or  pieces  ;  odorless  ;  taste 
sharp,  caustic.  In  contact  with  air  it  attracts  water  and  carbon 
dioxide,  and  falls  to  powder.  Soluble  in  750  parts  of  water  at 
.15°,  and  in  about  1,300  parts  of  boiling  water.  Insoluble  in 
alcohol. 

If  8  Gm  of  CaO  be  mixed  with  5  Gm  of  water  a  chemical  inter- 
action should  at  once  ensue,  and  the  calcium  hydroxide  formed 
should  be  completely  soluble  in  hydrochloric  or  nitric  acid. 


328  CALCIUM    PHOSPHATE. 

CALCIUM    PHOSPHATE. 

CALCII    PHOSPHAS    PRAECIPITATUS. 

[Precipitated  Tri-Calcium  Phosphate.] 
Ca3(P04)2=3io. 

Bone-ash  is  obtained  by  the  calcination  of  bones.  It  is  the 
inorganic  residue  left  on  burning  bones  to  whiteness,  and  consists 
mainly  of  tri-calcium  phosphate  with  about  ten  per  cent  of  cal- 
cium carbonate  and  a  little  calcium  fluoride  and  magnesium  phos- 
phate. It  is  used  in  the  manufacture  of  glacial  phosphoric  acid, 
precipitated  calcium  phosphate,  sodium  phosphate,  etc. 

It  should  be  white  or  but  slightly  grayish,  odorless,  and  almost 
completely  soluble,  with  but  slight  effervescence,  in  dilute  hydro- 
chloric acid. 

Precipitated  tri-calcium  phosphate  is  prepared  as  follows : 

Bone-ash,  in  fine  powder 300  Gm 

Hydrochloric  acid 450  ml 

Ammonia  water,  sufficient. 

Digest  the  bone-ash  with  the  acid,  diluted  with  1,500  ml  of 
water,  until  dissolved.  Boil  the  solution  a  few  minutes ;  filter ; 
then  add  1,500  ml  of  boiling  water.  Now  add  ammonia  water 
until  the  mixture  acquires  an  alkaline  reaction.  Collect  the  pre- 
cipitate on  a  muslin  strainer,  wash  it  with  hot  water  until  the 
washings  cease  to  produce  a  precipitate  with  test  solution  of 
silver  nitrate  acidulated  with  nitric  acid.  Dry  the  washed  pre- 
cipitate at  a  temperature  not  exceeding  100°  C. 

Reaction.  When  the  crude  tri-calcium  phosphate  is  dissolved 
in  hydrochloric  acid,  the  reaction  occurring  is  as  follows : 

Ca3  ( PO4)  2+4HCl=CaH4  ( PO4 )  2+2CaCl2. 

When  ammonia  is  added  to  the  solution  both  the  acid  calcium 
phosphate  and  the  calcium  chloride  are  decomposed, 

CaH4  ( PO4 )  2+2CaCl2+4H4NOH+ 
4H4NCl+4H20+Ca,  ( P04)  2. 


CALCIUM    PHOSPHATE.  329 

Notes.  Hot  liquids  are  employed  for  the  precipitation  in  order 
-M,at  the  product  may  be  dense  and  easily  washed.  If  the  pre- 
cipitation be  effected  in  cold  water  the  precipitated  calcium  phos- 
phate is  very  voluminous,  light,  presenting  a  gelatinous  appear- 
ance, and  the  washing  becomes  difficult. 

Description. — A  light,  white,  amorphous  powder;  odorless  and 
tasteless.  Insoluble  in  water  and  in  alcohol.  Assumes  a  yellow- 
ish color  when  moistened  with  silver-nitrate  test-solution. 


CALCIUM-HYDROGEN    PHOSPHATE. 

CALCII    PHOSPHAS    PRAECIPITATUS    CRYSTALLINUS. 

CaHPO4.2H2O=i72. 

Calcium  chloride u  paits 

Sodium  phosphate 36  parts 

Dissolve  the  calcium  chloride  in  100  parts  of  distilled  water,  and 
the  sodium  phosphate  in  200  parts.  Filter  each  solution.  Pour 
the  solution  of  calcium  chloride  into  the  solution  of  sodium  phos- 
phate, gradually  and  with  constant  stirring.  Wash  the  precipi- 
tate with  hot  distilled  water  by  decantation  and  finally  on  a, paper 
filter,  and  then  dry  the  product. 

Reaction.     Na2HPO4+CaCl2=2NaCl+CaHPO4. 

Notes.  If  hot  solutions  are  employed  the  precipitate  is 
easier  to  wash  because  it  will  then  be  more  compact.  Several 
pharmacopoeias  contain  this  calcium  phosphate  instead  of  the  tri- 
calcium  phosphate. 

Another  Method. 

Calcium  carbonate 10  parts 

Hydrochloric  acid 20  parts 

Distilled  water 65  parts 

Make  a  solution.  Add  to  it  a  sufficient  quantity  of  ammonia 
water  to  produce  an  alkaline  reaction  on  test-paper.  Filter. 

Pour  this  filtered  solution  of  calcium  chloride  thus  prepared 
into  a  solution  prepared  out  of : 


330  CALCIUM     PHOSPHATE. 

Sodium  phosphate 35  parts 

Distilled  water 200  parts 

Stirring  constantly.  Decant  the  mother-liquor.  Wash  the  pre- 
cipitate by  decantation  until  the  acidulated  washings  no  longer 
produce  a  precipitate  with  silver  nitrate  solution.  Dry  the 
product. 

Third  Method. 

Calcium  carbonate. . 20  parts 

Hydrochloric  acid  (32%  of  HC1) 40  parts 

Calcium  hydroxide I  part 

Phosphoric  acid  (85%  of  H3POJ 3  parts 

Sodium  phosphate - 61  parts 

Chlorine  water,  sufficient. 
Distilled  water,  sufficient. 

Mix  the  hydrochloric  acid  with  60  parts  of  distilled  water,  and 
add  the  calcium  carbonate.  When  effervescence  has  ceased  heat 
the  mixture  until  solution  is  effected. 

Let  the  liquid  cool  and  then  add  enough  chlorine  water  to  im- 
part a  distinct  odor  of  chlorine,  and  mix  well.  Heat  again  until 
the  odor  of  chlorine  ceases. 

Now  add  the  calcium  hydroxide,  stir  well,  and  let  the  mixture 
stand  for  half  an  hour  at  a  temperature  of  35°  to  40°  C. 

Filter  the  solution,  add  the  phosphoric  acid  to  the  filtrate,  filter 
again,  and  let  the  solution  get  cold. 

Dissolve  the  sodium  phosphate  in  300  parts  of  hot  distilled 
water,  filter  and  let  the  solution  cool  to  about  20°  C. 

Pour  the  solution  of  calcium  chloride  gradually  and  with  con- 
stant stirring  into  the  solution  of  sodium  phosphate. 

Let  the  mixture  stand,  stirring  frequently,  until  the  precipi- 
tate becomes  crystalline. 

Transfer  the  precipitate  to  a  cloth  strainer  and  wash  it  with 
distilled  water  until  the  washings  (acidulated  with  nitric  acid) 
no  longer  give  a  precipitate  with  silver  nitrate  test-solution. 

Let  it  drain  thoroughly;  squeeze  out  as  much  of  the  water  as 
practicable,  using  strong  pressure;  dry  the  precipitate  with  the 
aid  of  moderate  heat,  and  reduce  it  to  fine  powder. 

Description. — A  light,  white,  microcrystalline  powder ;  odorless, 
tasteless ;  insoluble  in  water  and  in  alcohol,  but  soluble  in  solution 
of  ammonium  citrate. 


CALCIUM   SULPHATE.  331 

Syrup  of  Calcium  Lactophosphate. 

Precipitated  calcium  carbonate 25  Gm 

Lactic  acid 60  ml 

Phosphoric  acid 36  ml 

Orange  flower  water 25  ml 

Sugar 700  Gm 

Water. 

To  the  lactic  acid  mixed  with  100  ml  of  water,  and  contained 
in  a  capacious  mortar,  gradually  add  the  calcium  carbonate,  in 
portions,  until  it  is  dissolved.  Then  add  the  phosphoric  acid,  and 
triturate  until  the  precipitate  at  first  formed  is  dissolved.  Add 
150  ml  of  water,  and  filter,  rinsing  the  mortar  with  75  ml  of 
water,  and  passing  the  rinsings  through  the  filter.  To  the  mixed 
filtrates  add  the  orange  flower  water,  and,  having  added  the 
sugar,  dissolve  it  by  agitation,  without  heat,  and  strain.  Lastly, 
pass  enough  water  through  the  strainer  to  make  the  product 
measure  1000  ml,  and  mix  thoroughly. 

CALCIUM    SULPHATE. 

CALCII   SULPHAS. 

CaSO4.2H2O=i72. 

Native  calcium  sulphate  or  "gypsum"  contains  two  molecules 
of  water.  From  it  the  dried  calcium  sulphate  or  "plaster"  is 
made. 

DRIED    CALCIUM    SULPHATE. 

[Surgical  "Plaster  of  Paris."] 

A  powder  containing  about  95  per  cent,  by  weight,  of  calcium 
sulphate  [CaSO4=i36],  and  about  5  per  cent  of  water;  pre- 
pared from  the  purer  varieties  of  native  gypsum  by  carefully  heat- 
ing until  about  three-fourths  of  the  water  has  been  expelled. 

Dried  calcium  sulphate  should  be  kept  in  well-closed  vessels, 
carefully  protected  from  moisture. 

Notes.  The  kind  of  dried  calcium  sulphate  required  is  one 
that  readily  takes  up  the  water  necessary  for  crystallization  and 


332  CALCIUM    SULPHIDE. 

at  once  sets  to  a  hard  mass.  An  anhydrous  calcium  sulphate  does 
not  do  this.  Hence  when  the  gypsum  is  dried  the  heat  must  not 
exceed  105°  C,  for  if  that  temperature  is  exceeded  the  product 
will  be  anhydrous  and  useless.  So-called  "dental  plaster  of 
paris"  is  well  adapted  for  surgical  plaster  bandages  and  casts.  It 
is  sold  by  dealers  in  dentists'  supplies. 

Description. — "Plaster  of  paris"  is  a  fine,  white  powder,  without 
odor  or  taste. 

From  moist  air  it  attracts  water,  becomes  granular,  and  then 
loses  the  property  of  hardening  with  water. 

When  mixed  with  half  of  its  weight  of  water,  dried  calcium 
sulphate  forms  a  smooth,  cohesive  paste,  which  rapidly  hardens. 

It  is  soluble  in  about  410  parts  of  water  at   15°  C. ;  in  388=J 
parts  at  38°  C.,  and  in  476  parts  at  100°  C.     In  alcohol  it  is  insol- 
ublc.  5  > 

'« 


CALCIUM    SULPHIDE;    CRUDE. 

CALX    SULPHURATA.  J>  G  'rv 

{.rr~T,  t^      \L'< 

Sulphurated  Lime. 

• 
m+> 

A  mixture  containing  at  least  60  per  cent  of  CaS. 

£__ 

Dried  calcium  sulphate,  in  fine  powder. . .   70  parts 

Charcoal,  in  fine  powder 10  parts 

Starch,  in  fine  powder 2  parts 

Mix  the  powders  thoroughly,  pack  the  mixture  lightly  into  a 
crucible,  cover  this  loosely,  and  heat  it  to  bright  redness,  continu- 
ing that  heat  until  the  contents  cease  to  have  a  black  color.  Let 
the  crucible  and  contents  cool.  Reduce  the  product  to  powder 
and  at  once  put  it  into  small  glass-stoppered  bottles. 

Reaction.     CaSO4+2C=CaS+2CO2 ;  and 
CaSO4+3C=CaS+2CO+CO2. 

Notes.  The  starch  seems  to  render  the  mixture  more  easily 
converted  by  the  heat.  The  reduction  is  not  complete,  and  the 


CALCIUM   SULPHITE.  333 

product  always  contains  calcium  sulphate  and  carbon,  amounting 
to  about  forty  per  cent. 

Description. — A  light  gray  powder  having  a  faint  odor  of  hy- 
drogen sulphide  and  a  nauseous  alkaline  taste.  Only  sparingly 
soluble  in  cold  water,  but  freely  soluble  in  boiling  water.  In- 
soluble in  alcohol.  Decomposed  by  hydrochloric,  nitric,  or  acetic 
acid  with  copious  evolution  of  hydrogen  sulphide;  the  undis- 
solved  residue  consists  of  calcium  sulphate  and  carbon. 


CALCIUM    SULPHITE. 

CALCII    SULPHIS. 

CaSO3.2H2O=i56. 

"Saturate  "milk  of  lime"  with  sulphur  dioxide  prepared  as  de- 
^S-ribed   under  the  title   Sulphur    Dioxide.      Filter  the   solution 
uahd  let  it  stand  exposed  to  the  air  until  the  crystals  of  calcium 
[jgilphite  have  deposited.     Collect  the  crystals  and  dry  them  be- 
3  rj:yeen  folds  of  blotting  paper. 
H     °P> 

f-y  ] 

H  Another  Method. 

>- .  i 

CD 

Calcium  chloride 2  parts 

Sodium  sulphite 5  parts 

Water. 

Dissolve  the  chloride  in  10  parts  of  water  and  the  sulphite  in 
50  parts.  Mix  the  solutions.  Wash  the  precipitate  with  cold 
water  and  dry  it  without  heat. 

This  calcium  sulphite  contains  no  water  and  is  amorphous. 
It  may  be  dissolved  in  a  saturated  solution  of  sulphurous  acid, 
adding  a  little  more  of  the  calcium  sulphite  to  the  acid  than  it  is 
able  to  dissolve,  filtering  this  solution  and  setting  it  aside  to  crys- 
tallize by  spontaneous  evaporation  on  exposure  to  the  air. 

Description. — White,  crystalline  powder,  very  sparingly  soluble 
in  water. 

The  solution  of  calcium  sulphite  in  sulphurous  acid  is  employed 
as  a  preservative  of  cider,  fruit  juices,  etc. 


334  CALCIUM  TETRATHIOSULPHATE. 

CALCIUM    TETRATHIOSULPHATE    SOLUTION. 

SOLUTION    OF    SULPHURATED    LIME. 

("Vlemingkx's  Solution.") 

Sublimed  sulphur 2  parts 

Lime i  part 

Water. 

Add  10  parts  of  water  to  the  lime  and  make  a  uniform  mixture 
of  them.  Dry  and  sift  the  sulphur,  add  it  to  the  lime  mixture, 
mix  well,  and  then  add  25  parts  of  water.  Boil  together  for  one 
hour,  stirring  constantly,  and  replace  the  water  lost  by  evapora- 
tion sufficiently  to  obtain  10  parts  of  finished  clear  solution.  Let 
settle  and  decant. 

Keep  the  product  in  well  closed  bottles. 

Notes.  The  solution  contains  calcium  sulphide  and  calcium, 
thiosulphate. 

The  reactions  are : 

CaO+H2O=Ca(OH)2;  and 
3Ca(OH)2+i2S=2CaSS4+CaSO3S+3H2O. 

It  will  be  found  that  the  theoretical  proportions  of  sulphur  and 
calcium  oxide  required  by  these  reactions  are  8  parts  of  sulphur 
and  7  parts  of  lime.  An  excess  of  sulphur  is,  however,  always 
employed.  Normal  calcium  sulphide  is  CaS,  and  a  solution  of  it 
dissolves  large  quantities  of  sulphur,  forming,  according  to  many 
authorities,  various  compounds.  The  chief  constituent  is,  how- 
ever, CaSS5,  or  calcium  tetrathiosulphate. 

Description. — A  dark  red-brown  liquid  having  an  odor  of  hy- 
drogen sulphide. 

CARBON. 
Purified  Animal  Charcoal. 

The  pharmacopceial  process  for  the  purification  of  animal  char- 
coal is  as  follows: 

Put  100  Gm  of  bone-black  into  a  capacious  flask,  and  add  200 
Gm  of  the  official  hydrochloric  acid  and  100  ml  of  boiling  water. 
Connect  the  flask  with  an  upright  condenser.  Apply  heat  by 


CARBON.  335 

means  of  a  sand-bath  to  the  flask  and  keep  the  contents  boiling 
gently  for  about  eight  hours.  Then  add  500  ml  of  boiling  water 
and  transfer  the  mixture  to  a  muslin  strainer.  When  the  liquid 
has  run  off,  return  the  charcoal  to  the  flask.  Add  to  it  100  ml 
of  hydrochloric  acid  and  the  same  quantity  of  boiling  water,  boil 
for  two  hours,  and  then,  again,  add  500  ml  of  boiling  water, 
transfer  the  mixture  to  a  plain  paper  filter,  and,  when  the  liquid 
has  passed  off,  wash  the  residue  with  boiling  water  until  the 
washings  no  longer  produce  a  precipitate  but  only  a  slight 
cloudiness  with  silver-nitrate  test-solution. 

Dry  the  washed  charcoal  perfectly  in  a  drying  oven,  and  im- 
mediately put  the  product  in  bottles  and  close  these  tightly. 

Notes.  The  hydrochloric  acid  removes  from  the  crude  animal 
charcoal,  or  bone-black,  all  of  the  calcium  phosphate  (a  little  over 
80  per  cent)  and  some  other  inorganic  substances,  but  leaves  to- 
gether with  the  carbon  the  siliceous  matter  (which  amounts  to 
about  4  per  cent.  The  product,  therefore,  is  less  than  16  per 
cent  of  the  weight  of  the  bone-black  used. 

If  the  bone-black  imparts  color  to  solution  of  KOH  when  boiled 
with  it,  it  has  not  been  completely  carbonized.  In  that  case  it 
should  be  treated  with  that  alkali  before  it  is  boiled  with  hydro- 
chloric acid.  The  bone-black  may  be  freed  from  animal  matter 
by  percolating  through  it  a  2  per  cent  solution  of  KOH  until  the 
liquid  passes  colorless,  and  then  water  until  the  percolate  be- 
comes tasteless. 

When  purified  animal  charcoal  has  been  kept  a  long  time  it  is  no 
longer  effective  as  a  decolorizing  agent,  but  can  be  renewed  by 
being  heated  to  dull  redness  in  a  covered  crucible  and  then  allowed 
to  cool. 

Description.  —  A  dull-black  odorless,  tasteless,  insoluble  powder. 
CARBON    DIOXIDE. 

CARBONEI    DIOXIDUM. 

[Carbonic  Acid  Gas.] 


Put  into  a  flask  a  convenient  quantity  of  marble  or  chalk,  in 
small  pieces,  and  add  enough  distilled  water  to  cover  it.     Con- 


336  CARBON  DIOXIDE. 

nect  this  generator  by  means  of  the  required  fittings  with  a  wash- 
bottle  containing  distilled  water,  and  provide  the  wash-bottle  with 
a  bent  glass  tube  for  conducting  the  gas  wherever  it  may  be  ne- 
cessary. Add  hydrochloric  acid  gradually,  through  a  safety  tube, 
to  the  marble  and  water. 

Reaction,     CaCO3+2HCl=CaCl2+H2O+CO2. 

Notes.  When  calcium  carbonate,  either  in  form  of  marble  or 
chalk,  is  used  for  generating  carbonic  acid  gas  by  double  decom- 
position with  hydrochloric  acid,  the  by-product  of  calcium  chloride 
may  be  recovered,  or  its  solution  may  be  used  for  the  preparation, 
of  precipitated  calcium  carbonate. 

When  sulphuric  acid  is  employed  instead  of  HC1,  calcium  sul- 
phate is  formed.  Chalk  and  sulphuric  acid  are  not  readily  mixed 
for  making  carbonic  acid  in  the  manufacture  of  mineral  waters 
on  a  large  scale,  owing  to  the  fact  that  the  whiting  used  contains 
enough  moisture  to  render  it  lumpy,  so  that  a  portion  of  it  is  not 
acted  upon  by  the  acid.  Chalk,  moreover,  contains  animal  and 
bituminous  matters,  and,  therefore,  yields  an  impure  carbonic 
acid  gas  of  disagreeable  odor  and  taste,  which  are  with  great  dif- 
ficulty removed.  Chalk  is  nevertheless  very  generally  employed, 
and  sulphuric  acid  is  used  in  preference  to  hydrochloric  acid,  be- 
cause the  latter  is  not  only  dearer  but  requires  a  larger  acid 
chamber.  The  reaction,  when  chalk  (whiting)  and  sulphuric 
acid  are  the  materials  used,  is: 

CaC08+H2S04=CaS04+H20+COa. 

The  prompt  removal  of  the  calcium  sulphate  from  the  generator 
as  soon  as  the  chalk  has  been  consumed,  is  necessary,  in  view  of 
the  fact  that  a  hard  mass  is  soon  formed  by  the  residue,  which 
will  be  found  troublesome  to  remove. 

Assuming  that  the  chalk  used  contains  90  per  cent  of  CaCO3, 
and  the  sulphuric  acid  92  per  cent  of  HoSO4,  it  will  require  10,- 
ooo  parts  of  chalk  and  9,600  parts  of  acid  to  produce  3,960  parts  of 
CO2.  At  20°  C.  3,960  Gm  of  carbonic  acid  gas  measures  2,200 
liters. 

Sodium  bicarbonate  furnishes  a  purer  carbonic  acid  gas  than  can 
be  obtained  from  chalk. 

Carbonic  acid  water,  .or  so-called  "soda  water,"  is  water  sat- 


CARBON  DISULPHIDE.  337 

urated  with  carbonic  acid  under  about  50  pounds  pressure  and  at 
nearly  the  freezing  point.  It  is  now  prepared  most  conveniently 
from  compressed  carbon  dioxide  in  liquid  form  which  is  manu- 
factured and  sold  in  cylinders. 

Water  at  o°  C.  dissolves,  under  the  ordinary  atmospheric  pres- 
sure, 1.8  times  its  own  volume  of  CO2.  Under  the  pressure  of 
three  atmospheres  (45  pounds  to  the  square  inch),  one  volume 
of  water  dissolves,  at  o°  C.,  5.4  volumes  of  CO2. 

CARBON    DISULPHIDE. 

CARBONEI    DISULPHIDUM. 

(Bisulphide  of  Carbon.) 
CS2=76. 

A  clear,  colorless,  highly  refractive,  very  diffusive  liquid,  having 
a  strong,  characteristic,  but  not  fetid,  odor,  and  a  sharp,  aromatic 
taste.  Miscible  in  all  proportions  with  alcohol,  ether,  chloroform, 
fixed  oils,  and  volatile  oils.  Sp.  w.  1.268  to  1.269  at  I5°-  Prac- 
tically insoluble  in  water. 

It  must  be  kept  in  tightly  stoppered  bottles,  not  more  than 
three-fourths  filled,  or  in  tin  cans,  in  a  cool  place,  remote  from 
fire. 

CERIUM    NITRATE. 

CERII    NITRAS. 

Ce(N03)3.6H20=433. 

Dissolve  eerie  oxide  in  dilute  nitric  acid  and  evaporate  to  crys- 
tallization. It  may  also  be  made  from  cerous  sulphate  and  barium 
nitrate. 

Description. — Colorless  crystals,  freely  soluble  in  water  and  in 
alcohol. 

CERIUM    OXALATE. 

CERII    OXALAS. 

Ce2(C204)3.9H20= 704. 

Silicate  of  cerium  exists  in  the  minerals  cerite  and  allanite. 
From  these  minerals  the  cerium  sulphate  is  first  prepared;  then 

Vol.   11—22 


338  CERIUM   OXIDE. 

other  salts  are  made  from  the  sulphate.     The  oxalate  is  made 
from  the  cerous  sulphate  and  sodium  oxalate. 

Description. — A  white  powder,  tasteless  and  insoluble  in  water, 
but  readily  soluble  in  dilute  acids. 


CERIUM    OXIDE. 

CERII   OXIDUM. 

CeD2=i7i. 

Heat  cerium  oxalate  in  a  Hessian  crucible  to  redness  and  let 
the  contents  cool. 

Description. — A  reddish  powder ;  insoluble  in  water. 
CERIUM    SULPHATE. 

CERII    SULPHAS. 

Ce2(S04)  3=566. 

Ceric  oxide  is  dissolved  in  sulphuric  acid. 
The  eerie  sulphate  may  be  reduced  to  cerous  sulphate  by  means 
of  sodium  thiosulphate. 

Description. — Colorless ;  soluble  in  water. 
CHLORINE. 

CHLORUM. 

Cl2=;o.8. 

Manganese  dioxide 10  parts 

Hydrochloric  acid 35  parts 

Water 25  parts 

As  a  generator  use  a  flask  of  ample  capacity  and  provided  with 
well  fitting  perforated  rubber  stopper  carrying  the  thistle  tube, 
safety  tube  and  delivery  tube.  Connect  the  generator  in  the 
usual  way  with  a  wash-bottle  containing  water,  and  having  a 


CHLORINE.  339 

delivery  tube  which  may  be,  in  turn,  connected  with  the  vessel 
into  which  the  chlorine  gas  is  to  be  conducted. 

The  manganese  dioxide  must  be  coarsely  powdered  and  the 
fine  powder  removed  from  it.  It  is  put  in  the  generator,  all  con- 
nections are  made  tight,  and  then  the  mixture  of  acid  and  water 
poured  into  the  flask  through  the  thistle  tube. 

The  flask  is  then  heated  by  means  of  a  Bunsen  burner  and  sand- 
bath  until  the  evolution  of  chlorine  begins  (at  about  50°  C). 
The  burner  may  then  be  withdrawn  to  be  replaced  again  only 
when  the  reaction  seems  so  slow  as  to  require  it. 

The  chlorine  is  washed  by  passing  it  through  water. 

Keaction.     MnO2+4HCl=MnCl2+H2O+Cl2. 

Notes.  See  Chlorine  Solution.  The  hydrochloric  acid  may  be 
added  gradually  as  required  and  further  addition  discontinued 
when  no  further  evolution  of  chlorine  is  desired.  To  stop  the  liber- 
ation of  chlorine  entirely  the  liquid  in  the  flask  is  poured  off  from 
the  remaining  manganese  dioxide.  This  liquid,  containing  man- 
ganese chloride,  may  be  reserved  for  the  recovery  of  the  salt 
from  it. 

Kipp's  apparatus  may  be  used  to  advantage. 

Chlorine  Solution. 
(CHLORINE  WATER.) 

A  water-solution  of  chlorine  containing  not  less  than  0.4  per 
cent  of  that  element.  This  is  not  a  saturated  solution,  but  it  is 
sufficiently  strong,  and  it  would  be  difficult  to  comply  with  a  re- 
quirement of  greater  chlorine  strength  because  water  is  decom- 
posed by  chlorine,  hydrochloric  acid  being  formed,  and  a  stronger 
solution  deteriorates  more  rapidly.  A  saturated  solution  at  15° 
C.  contains  about  0.6  per  cent  of  C12. 

Apparatus  required.  A  flask  of  about  500  ml  capacity ;  a  sand- 
bath  and  Bunsen  burner;  a  Woulff  bottle  of  about  one  liter's 
capacity ;  two  glass-stoppered  receiving-bottles,  each  of  one  liter's 
capacity;  glass  tubing,  perforated  rubber  stoppers,  rubber  tube 
connections,  and  safety  tubes ;  and  glass-stoppered  containers  of 
amber-colored  glass  and  of  200  or  at  most  250  ml  capacity. 

The  flask  to  be  used  as  the  generator,  the  Woulff  bottle  in  which 


34O  CHLORINE. 

the  gas  is  washed,  and  one  of  the  receiving-bottles  are  connected 
by  means  of  the  stoppers  and  tubing,  and  provided  with  the  safety 
tubes. 

A  vessel  of  water  is  also  necessary  in  which  the  receivers  may 
be  placed  to  cool  them  with  the  aid  of  crushed  ice. 

Materials.  Coarsely  powdered  manganese  dioxide,  freed  from 
fine  powder,  20  Gm ;  official  hydrochloric  acid ;  distilled  water 
which  has  been  boiled  a  few  minutes  and  allowed  to  cool  again ; 
a  sufficient  quantity  of  ice ;  and  some  loose  cotton. 

Process.  Put  the  manganese  dioxide  (20  Gm)  into  the  flask 
and  place  this  on  the  sand-bath. 

Put  about  1 20  ml  of  water  into  the  wash-bottle. 

Put  400  ml  of  water  into  each  receiving-bottle. 

Place  one  of  the  receiving-bottles  in  the  vessel  of  water  kept 
at  a  temperature  of  about  10°  C.  by  means  of  the  ice,  and  put  into 
the  neck  of  that  bottle  some  loose  cotton  around  the  glass  tube 
through  which  the  chlorine  is  to  enter  it. 

Now  pour  into  the  flask  or  generator,  through  the  thistle  tube, 
a  mixture  of  70  ml  of  hydrochloric  acid  and  50  ml  of  water. 

Apply  gently  heat  to  the  sand-bath  so  as  to  warm  the  flask. 
Increase  the  heat  gradually,  so  that  the  liberation  of  chlorine 
may  proceed  rapidly  enough'  but  not  violently.  The  chlorine  is 
to  be  passed  through  the  water  in  the  wash-bottle  and  then  from 
the  upper  part  of  that  bottle  into  the  receiver. 

When  the  air  in  the  receiving-bottle  shall  have  been  wholly  dis- 
placed by  the  greenish-yellow  chlorine  gas,  remove  the  bottle,  close 
it  with  its  glass  stopper,  and  put  the  second  receiving-bottle  (con- 
taining, like  the  first,  400  ml  of  boiled  and  cooled  water)  in  its 
place. 

Shake  well  the  receiving  bottle  just  removed  so  that  the  chlor- 
ine may  be  dissolved  in  the  water. 

Continue  the  evolution  of  chlorine  and  collect  the  washed  gas 
as  before,  exchanging  the  two  receiving-bottles,  alternately,  in 
the  manner  described,  until  the  water  in  both  shall  have  become 
thoroughly  saturated  with  chlorine. 

Then  pour  the  saturated  solution  into  the  amber-colored  stock- 
bottles,  filling  each  of  them  completely,  close  the  filled  bottles 
tightly  by  their  glass  stoppers,  and  keep  them  in  a  cool,  dark 
place. 


CHLORINE.  341 

Reaction.    MnO2+4HCl=MnCl2+2H2O+Cl2. 

Notes.  The  use  of  a  too  finely  powdered  manganese  dioxide 
would  result  in  a  too  rapid  evolution  of  gas. 

The  use  of  undiluted  hydrochloric  acid  causes  the  reaction  to 
begin  at  once  without  the  application  of  heat;  but  it  would  not 
continue  to  the  end.  Experience  has  taught  that  a  diluted  acid, 
as  directed,  is  preferable.  The  reaction  can  be  readily  controlled 
by  proper  regulation  of  the  heat  applied. 

The  temperature  of  the  water  in  the  receiving  bottles  should 
not  be  permitted  to  fall  below  9°  C.  because  the  water  dissolves 
the  chlorine  most  readily  and  in  greatest  proportion  at  about 
9°  to  10°.  Should  the  temperature  at  which  chlorine  water  is 
prepared  (out-doors)  be  as  low  as  about  i°  to  3°  C.,  or  should 
the  water  in  the  receiving  bottle  be  as  cold  as  that,  it  may  cause 
the  formation  of  crystals  of  Cl2-f-ioH2O.  If  these  crystals 
are  formed  in  the  tube  connections  these  may  be  closed. 

Caution.  The  operator  should  not  forget  that  chlorine  gas  is 
poisonous  when  inhaled  in  such  quantities  as  to  prove  irritating  to 
the  respiratory  organs.  Hence  sufficient  precautions  must  be 
taken  to  prevent  injury.  It  is  best  to  make  chlorine  water  under  a 
hood  or  fume  chamber,  or  out-of-doors. 

Should  any  accident  occur  whereby  the  chlorine  is  caused  to 
escape  into  the  room  to  such  an  extent  as  to  cause  irritation  or 
danger,  the  operator  should  at  once  neutralize  its  effects  with 
ammonia.  Should  any  person  inhale  chlorine,  let  a  little  am- 
monia be  cautiously  inhaled,  too,  and  afterwards  a  little  alcohol 
or  ether. 

Preservation.  Chlorine  water  must  be  kept  in  comparatively 
"small  bottles"  because  it  does  not  deteriorate  so  rapidly  when 
not  in  contact  with  air,  or,  in  other  words,  when  the  containers 
are  filled.  It  must  be  kept  in  a  cool  and  dark  place  because  a 
higher  temperature  would  cause  the  expulsion  of  the  gas  from 
its  solution  and  might  even  cause  a  completely  filled  bottle  to  burst 
from  the  pressure,  and  light  greatly  hastens  the  formation  of  hy- 
drochloric acid. 

But  chlorine  water  should  not  be  kept  in  a  place  where  the 
temperature  is  below  4°.  C. 


342  CHLORINATED  LIME. 

Description. — A  greenish-yellow  liquid  having  the  peculiar  suf- 
focating odor  and  disagreeable  taste  of  chlorine.  It  decolorizes 
dilute  solutions  of  litmus,  indigo  and  other  vegetable  coloring 
matters. 

Chlorinated  Lime. 

(Bleaching  Powder.     "Chloride  of  Lime.") 

A  slightly  grayish  white,  or  quite  white,  granular,  dry  powder, 
evolving  the  odor  of  hypochlorous  acid  (a  somewhat  chlorine-like 
odor).  It  has  a  nauseous,  acrid,  saline  taste.  Very  hygroscopic. 
Decomposes  on  exposure  to  air.  Only  partially  soluble  in  water. 
Reacts  with  alcohol  and  with  glycerin. 

Its  principal  or  most  important  constituent  is  calcium  hypo- 
chlorite,  Ca(OCl)2  which  readily  decomposes  on  the  addition  of 
an  acid,  giving  off  free  chlorine.  The  chlorine  thus  liberated  is 
termed  the  "available  chlorine"  of  the  chlorinated  lime,  and  the 
American  Pharmacopoeia  requires  the  preparation  to  contain  and 
produce  not  less  than  35  per  cent  of  available  chlorine. 

Calcium  chloride  constitutes  a  large  proportion  of  the  chlorin- 
ated lime. 

Bleaching  powder  is  produced  by  the  action  of  chlorine  on 
slaked  lime. 

Chlorinated  lime  must  be  kept  in  tightly  closed  vessels,  to  com- 
pletely exclude  air  and  moisture,  and  should  be  stored  in  a  cool, 
dry  place. 

When  damp  the  chlorinated  lime  should  be  rejected. 

It  is  largely  used  as  a  bleaching  agent  and  as  a  disinfectant. 

To  produce  chlorine  gas  for  purposes  of  disinfection,  chlorin- 
ated lime  may  be  put  in  a  dish,  mixed  with  some  diluted  acid  or 
vinegar,  and  placed  in  the  room  which  is  then  kept  closed  for  a 
sufficient  period. 

CHROMIUM   ACETATE. 

CHROMII   ACETAS. 
Cr(C2H3O2)3=229. 

Chrome  alum . .  10  parts 

Sodium  carbonate 9  parts 

Acetic  acid  (36% ) 10  parts 

Water. 


CHROME  ALUM.  343 

Dissolve  the  chrome  alum,  in  40  parts,  and  the  sodium  carbonate 
in  20  parts  of  water.  Add  the  sodium  carbonate  solution  to  the 
chrome  alum,  stirring  well.  Wash  the  chromium  hydroxide  with 
warm  water  by  decantation.  Drain  well,  and  dissolve  it  in  the 
acetic  acid  with  the  aid  of  moderate  heat.  Evaporate  to  dryness. 

Reaction. 

2KCr  ( S04)  2+3Na2C03+3H20 

=K2SO4+3Na2SO44-2Cr(OH)3+3CO2;  and  then 
Cr(OH)3+3HC2H302-Cr(C2H302)3+3H20. 

Description. — A  greenish,  very  soluble  salt,  extremely  difficult 
to  crystallize.  The  solution  when  made  below  60°  is  violet,  but  it 
becomes  greenish  when  heated. 

CHROME   ALUM. 

ALUMEN    CHROMICUM. 

KCr(SO4)2.i2H2O=499. 

Potassium  dichromate 4  parts 

Sulphuric  acid  (92.5%  of  H2SO4) 5  parts 

Water 9  parts 

Starch   I  part 

Put  the  water  in  a  large  enough  porcelain  dish  to  hold  at  least 
twice  the  total  quantities  operated  upon.  Set  the  water  into  rapid 
rotary  motion  by  stirring  with  a  glass  rod.  Add  the  sulphuric 
acid  in  a  thin  stream.  Dissolve  the  potassium  dichromate  in  the 
mixture.  Then  add  the  starch  a  small  quantity  at  a  time,  stir- 
ring cautiously.  When  the  reaction  is  nearly  ended,  heat  the 
liquid,  //  necessary,  until  it  acquires  a  bluish-green  color.  Filter 
the  solution  and  set  it  in  a  -cold  place  to  crystallize.. 

Reaction. 

2K2Cr207+8H2S04+3C+4oH2O=4[KCr(S04)2.i2H20]-f 
3C02. 

Notes.  The  temperature  of  the  reaction  is  very  high,  and  the 
chemical  interaction  liable  to  be  violent  unless  the  starch  be  added 
very  slowly.  It  is  necessary  that  the  mixture  should  remain  hot 


344  CHROMIC  ANHYDRIDE. 

throughout  the  whole  reaction,  but  no  application  of  heat  from 
without  is  necessary,  nor  should  it  be  resorted  to  until  after  the 
violence  of  the  action  has  subsided.  The  liquid  must  at  the  end  be 
bluish-green,  and  not  olive-green.  Should  the  bluish-green  color 
be  attained  without  the  application  of  heat,  no  heating  is  neces- 
sary. Should,  on  the  other  hand,  the  liquid  be  olive  green,  heat  it 
cautiously  until  it  acquires  a  bluish-green  color. 

In  case  the  crystallization  should  be  much  retarded,  evaporate 
the  solution  somewhat,  and  then  set  it  in  a  cold  place.  Should 
it  still  fail  to  crystallize  drop  into  it  a  few  crystals  of  chrome 
alum  to  start  the  crystallization. 

As  the  salt  is  efflorescent  it  must  be  kept  in  tightly  closed  bot- 
tles in  a  cool  place. 

Description. — Dark  purple,  transparent  crystals,  soluble  in  7 
parts  of  water  at  15°.  The  cold  solution  is  reddish-blue,  but 
above  70°  it  becomes  bluish-green. 


CHROMIC   ANHYDRIDE. 

"ACIDUM  CHROMICUM." 

["Chromic  Acid."     U.  S.] 

CrO3=ioo. 

Potassium  dichromate 3  parts 

Sulphuric  acid  (92.5%  of  H2SO4) 11  parts 

Nitric  acid  (68%  of  HNO3). 
Water. 

Put  5  parts  of  water  in  a  porcelain  dish  capable  of  holding  about 
ten  times  that  quantity ;  set  this  water  into  rotary  motion  by  brisk 
stirring  with  a  glass  rod.  Add  slowly  and  in  a  small  stream  8.5 
parts  of  the  sulphuric  acid.  Dissolve  the  coarsely  powdered  po- 
tassium dichromate  in  the  mixture,  applying  gentle  heat  to  facili- 
tate the  solution.  Let  the  liquid  stand  (at  the  ordinary  room 
temperature)  for  about  twelve  hours  in  the  dish,  which  should  be 
covered  to  keep  out  dust.  A  mass  of  crystals  of  acid  potassium 
sulphate  will  now  be  found  on  the  bottom  of  the  dish. 

Decant  the  red  liquid  from  the  crystals.     Heat  it  in  a  large 


CHROMIC  ANHYDRIDE.  345 

porcelain  dish  to  a  temperature  of  from  80°  to  90°  ;  and  then  add 
slowly  the  remainder  (2.5  parts)  of  the  sulphuric  acid. 

Should  any  dark-red  crystals  of  chromic  anhydride  have  formed 
in  the  liquid,  add  cautiously  just  enough  water  to  cause  them  to 
be  redissolved. 

Let  the  liquid  cool  and  set  it  aside  for  twelve  hours.  Pour  off 
the  mother-liquor  from  the  crystals  of  chromic  anhydride.  Place 
•  the  mass  of  crystals  in  a  funnel  and  let  it  be  well  drained.  Then 
spread  the  crystals  out  upon  porous  tiles  and  leave  them  there  for 
an  hour,  after  which  transfer  them  to  a  funnel  again  and  rinse 
them  a  few  times  with  small  quantities  of  cold  concentrated  nitric 
acid.  Again  place  the  crystalline  mass  upon  fresh  porous  tiles 
and  let  it  remain  on  the  tiles  for  an  hour  or  two.  Then  drive  off 
the  remaining  nitric  acid  adhering  to  the  crystals  by  heating  them 
in  a  porcelain  dish  at  from  80°  to  90°.  Put  the  product  at  once  in 
glass-stoppered  bottles. 

The  mother-liquor  poured  off  from  the  first  crop  of  crystals 
may  be  concentrated  by  evaporation  and  set  aside  to  deposit  an 
additional  crop  of  crystals  of  chromic  anhydride,  which  must  be 
drained  and  otherwise  treated  in  the  same  manner. 

Reaction.     K2Cr2O7+2H2SO4=2CrO3+2KHSO4-fH2O. 

Notes.  It  will  be  seen  that  the  quantity  of  sulphuric  acid  pre- 
scribed is  several  times  as  great  as  that  required  according  to  the 
equation.  This  is  necessary  to  cause  the  chromic  anhydride  to 
crystallize  out.  The  crystals  can  not  be  drained  sufficiently  free 
from  sulphuric  acid,  nor  can  they  be  washed  with  water  or  recrys- 
tallized;  but  they  can  be  washed  with  strong  nitric  acid,  which 
does  not  affect  the  chromic  anhydride,  and  the  adhering  nitric  acid 
can  be  gotten  rid  of  by  evaporation. 

Description. — Small,  needle-shaped  crystals,  of  a  dark-red  color, 
with  a  suggestion  of  purplish  hue,  and  of  somewhat  metallic  lustre. 
Odorless.  Deliquescent.  Corrosive,  and  a  very  powerful  oxidiz- 
ing agent.  It  is  destructive  to  animal  and  vegetable  tissues,  and, 
therefore,  an  escharotic.  It  should  not  be  brought  in  contact  with 
reducing  agents  such  as  tannin,  sugar,  alcohol,  glycerin,  etc.,  as 
dangerous  accidents  might  occur  from  the  violent  reactions  liable 
to  take  place.  Very  soluble  in  water. 


346  CHROMIUM   HYDROXIDE. 

Solution  of  Chromic  Acid;  B.P. 

The  British  Pharmacopoeia  contains  a  formula  for  a  solution 
of  chromic  acid.  It  directs  the  solution  of  i  part  of  chromic  an- 
hydride in  3  parts  of  distilled  water.  This  solution  has  the  sp.  w. 
1.185  and  its  strength  is  29.5  per  cent  expressed  in  terms  of 
chromic  acid  (H2CrO4),  corresponding  to  25  per  cent  of  chromic 
anhydride  (CrO3). 

CHROMIUM   HYDROXIDE. 

CHROMII   HYDROXIDUM. 

Cr(OH)3=io3. 

Prepared  from  chrome  alum  as  described  under  the  head  of 
chromium  acetate. 

It  may  also  be  prepared  from  chromium  sulphate,  as  follows : 

Chromium  sulphate 2  parts 

Ammonia  water  ( 10%  ) 3  parts 

Water. 

Dissolve  the  chrome  alum  in  an  equal  weight  of  water,  and  add 
the  ammonia.  Boil  for  twenty  minutes.  Wash  and  dry  the  pre- 
cipitate. 

Chromium  hydroxide  may  also  be  prepared  by  conducting  a 
strong  current  of  hydrogen  sulphide  into  a  solution  of  potassium 
dichromate  until  the  precipitate  formed  becomes  green,  and  then 
washing  and  drying  it ;  but  this  product  contains  much  sulphur. 

Description. — A  green,  insoluble  powder. 

CHROMIUM   SULPHATE. 

CHROMII  SULPHAS. 

Cr2(SO4)3.i5H2O=662. 

Dissolve  24  parts  of  dry  chromium  hydroxide  in  25  parts  of 
sulphuric  acid  of  92.5%  strength  in  a  porcelain  dish  at  a  tempera- 
ture of  about  40°  to  50°.  A  violet  solution  is  obtained  from  which 
crystals  are  obtained  on  cooling.  The  temperature  must  not  be 


COPPER  ACETATE. 


347 


permitted  to  exceed  60°  at  any  time,  as  the  solution  then  becomes 
green  and  does  not  yield  any  crystals  until  after  standing  for 
several  weeks. 

It  is  said  that  the  addition  of  some  dilute  alcohol  to  the  purple 
solution  of  chromic  sulphate  facilitates  the  crystallization  of  the 
salt. 

Description. — Purple  or  violet  crystals,  soluble  in  less  than  their 
own  weight  of  water. 

COPPER  ACETATE. 

CUPRI  ACETAS. 

Cu(C2H302)2.H20=  199.5. 

Subacetate  of  copper 100  Gm 

Diluted  acetic  acid 400  ml 

Water    200  ml 

Triturate  the  verdigris  with  enough  water  to  form  a  smooth, 
thin  paste.  Then  add  the  acid,  mix  well,  transfer  the  mixture  to 
a  porcelain  capsule,  and  heat  it  over  a  water-bath  at  not  over  80° 
C.  -(176°  F.)  until  solution  is  effected.  Filter  while  hot.  Set 
aside  to  cool  and  crystallize.  Collect  and  dry  the  crystals  on  blot- 
ting paper  in  a  cool  place. 

Reaction.    Cu2O  ( C2H3O2 )  2+2HC2H3O2+H2O 

=2(Cu(C2H302)2.H20). 

Notes.  To  obtain  good  crystals  a  slight  excess  of  acetic  acid 
must  be  present  during  the  evaporation  and  crystallization.  Should 
the  liquid  become  unclear  from  blue  di-basic  copper  acetate, 
through  loss  of  acetic  acid  by  evaporation,  more  acid  must  be! 
added. 

Additional  crops  of  crystals  can  be  obtained  from  the  mother 
liquor  on  evaporation. 

The  total  product  should  be  at  least  equal  to  the  weight  of  the 
verdigris  used.  The  crystals  should  be  distinct,  deep  green,  and 
should  make  perfectly  clear  solutions  with  water,  or  with  ammonia 
water. 

Must  be  kept  in  a  well  corked  bottle,  and  in  a  cool  place. 


348  COPPER  ACETATE. 

Second  Method. 

Copper  sulphate 2  parts 

Lead  acetate 3  parts 

Acetic  acid,  sufficient. 

Dissolve  each  salt  separately  in  6  parts  of  water.  If  necessary 
add  a  little  acetic  acid  to  the  solution  of  the  lead  acetate  to  render 
it  clear.  Filter  the  solutions.  Mix  them.  Filter.  Collect  the 
filtrate  containing  the  copper  acetate,  evaporate  it  on  a  water-bath 
at  not  over  80°  C.  (176°  F.)  until  a  pellicle  begins  to  form,  taking 
care  to  keep  acetic  acid  present  in  excess.  Then  set  aside  to  crys- 
tallize. 

Reaction.     CuSO4.5H2O+Pb(C2H3O2)23H2O= 

Cu  ( C2H8O2)  2.H2O+PbSO4+7H2O 

Third  Method. 

Copper  sulphate 25  parts 

Solution  of  sodium  hydroxide  (5  per  cent)  .  .  165  parts 

Acetic  acid  (36  per  cent  of  HC2H3O2) 36  parts 

Water. 

Dissolve  the  copper  sulphate  in  250  parts  of  water  and  filter. 
Pour  this  solution  into  the  solution  of  sodium  hydroxide,  stirring 
briskly.  Wash  the  precipitated  copper  hydroxide  thoroughly  by 
affusion  and  decantation  of  water  until  the  washings  are  tasteless. 
Let  it  drain.  Put  the  moist  copper  hydroxide  in  a  porcelain  dish. 
Add  the  acetic  acid.  Heat  gently  until  solution  is  effected.  Evap- 
orate to  crystallization,  taking  care  to  keep  an  excess  of  acetic  acid 
present  in  the  liquid. 

Fourth  Method. 

Copper  acetate  may  also  be  prepared  by  adding  a  solution  of 
copper  sulphate  to  one  of  barium  acetate  until  no  further  precip- 
itation results.  Care  should  be  taken  to  add  neither  more  nor  less 
than  is  necessary.  The  liquid  must  be  well  stirred  and  set  aside 
for  a  day  or  two  before  it  is  filtered  and  the  filtrate  evaporated  to 
crystallization. 

reaction.    CuSO4  +Ba ( C2H;!O2) 2=Cu ( C2H3O2)  2+BaSO4. 


COPPER   CHLORIDE.  349 

Notes.  Handsome  rhombic  crystals  of  normal  cupric  acetate 
with  5  molecules  of  water  are  formed  if  a  solution  saturated  at 
60°  C.  is  rapidly  cooled  ;  when  warmed  to  about  30°  C.  these  crys- 
tals lose  4  molecules  of  water  and  turn  green  and  opaque,  but 
retain  their  form. 

Copper  acetate  readily  loses  acetic  acid  and  water,  becoming 
basic,  insoluble  and  blue  or  light  green.  Hence  the  necessity  of 
keeping  the  salt  in  a  tightly  closed  bottle  in  a  cool  place. 

In  the  process  of  preparation  it  should  not  be  exposed  to  the  air 
and  to  heat  any  more  than  is  unavoidable. 

Description.  —  Dark  green  crystals  with  metallic  taste  and  ace- 
tous odor.  Completely  soluble  in  water,  and  difficultly  soluble  in 
alcohol. 

COPPER  CHLORIDE. 

CUPRI  CHLORIDUM. 


Saturate  hydrochloric  acid  with  freshly  precipitated  and  well 
washed  copper  subcarbonate  (made  from  cupric  sulphate  with 
sodium  carbonate)  .  Evaporate  the  solution  to  the  density  of  about 
i.  44.  and  set  it  in  a  cool  place  to  crystallize. 

It  may  also  be  made  from  cupric  sulphate  and  barium  chloride 
by  metathesis. 

Description.  —  Slender,  green,  deliquescent  crystals,  soluble  in 
less  than  their  own  weight  of  water. 

COPPER  NITRATE. 

CUPRI   NITRAS. 

Cu(NO3)2.3H2O=24i. 

Copper  sulphate  ......................   25  parts 

Barium  nitrate   ..................  .....   26  parts 

Dissolve  the  copper  sulphate  in  200  parts  of  water  and  the  bar- 
ium nitrate  in  300  parts  of  water.  Filter  the  solutions.  Pour  the 
solution  of  barium  nitrate  into  the  solution  of  copper  sulphate, 


35O  COPPER   NITRATE. 

stirring  well.  Reject  the  precipitated  barium  sulphate.  Filter  the 
solution  of  copper  nitrate,  acidify  it  with  nitric  acid,  and  evaporate 
it  to  obtain  the  product  in  crystals. 

Redissolve  the  crystals  in  distilled  water,  acidify  with  nitric 
acid,  and  recrystallize. 

Reaction.    CuSO4.sH2O+Ba  ( NO3)  2=Cu  ( NO3 )  2.3H2O 

+BaSO42H2O. 

Another  Method. 

Copper  nitrate  may  also  be  made  by  saturating  diluted  nitric 
acid  with  metallic  copper,  and  crystallizing  at  about  25°  C. 

Reaction.    3Cu-f  8HNO3=3Cu  ( NO3 )  2+4H2O+2NO. 

Description. — Beautiful,  transparent,  deep-blue  crystals,  readily 
soluble  in  water. 


COPPER  OLEATE. 

CUPRI   OLEAS. 

Cu(C18H33O2)  2=625.5. 

Copper  sulphate 60  Gm 

White  castile  soap,  in  fine  powder 150  Gm 

Dissolve  the  copper  sulphate  in  five  liters  of  water,  and  the  soap 
in  three  liters  of  hot  water.  Pour  the  soap  solution  into  that  of 
the  copper  sulphate,  stirring  well.  Wash  the  precipitated  oleate 
twice,  using  ten  liters  of  hot  water  each  time.  Collect  the  dark- 
green  oleate,  squeeze  the  water  out  of  it,  and  fuse  it  by  very  gentle 
heat,  over  the  water-bath. 

Reaction.     CuSO4+2NaC18H33O2=Cu(C18H33O2)2+Na2SO4. 

Notes.  The  product  is  about  290  Gm  of  a  dark-green,  waxy 
plaster,  containing  12.67  Per  cent  °f  copper  oxide. 


COPPER  OXIDE.  351 

COPPER   OXIDE. 

CUPRI  OXIDUM. 


Heat  copper  nitrate  strongly  until  no  more  red  vapors  pass  off 
and  the  residue  is  a  fine,  black  powder. 

2Cu(NO3)2=2CuO+2N2O4+O2. 

Cupric  oxide  is  insoluble  in  water,  but  readily  soluble  in  dilute 
hydrochloric,  nitric,  sulphuric  and  acetic  acids. 


COPPER    SUBCARBONATE. 

CUPRI     SUBCARBONAS. 

Cupric  sulphate  .............  ,  .........   5  parts 

Sodium  carbonate   .....................   6  parts 

Water. 

Dissolve  the  blue  vitriol  in  20  parts  of  hot  water  and  filter.  Dis- 
solve the  sodium  carbonate  also  in  20  parts  of  water  and  filter. 
Add  the  hot  copper  solution  slowly  or  in  small  portions  to  the  hot 
sodium  carbonate  solution  in  a  large  vessel,  being  careful  not  to 
let  the  liquid  run  over  from  the  active  effervescence.  Wash  the 
precipitate  with  hot  water  by  decantation  and  then  dry  it. 

Description.  —  A  green  powder  having  a  variable  composition. 
Insoluble  in  water  but  readily  soluble  in  acetic,  sulphuric,  hydro- 
chloric and  nitric  acids. 

COPPER  SULPHATE. 

CUPRI    SULPHAS. 

CuS04.5H20=249.5. 

Copper,  in  filings  .....................  5  parts 

Sulphuric  acid   .......................  8  parts 

Nitric  acid   ..........................  4  parts 

Water    ..............................  30  parts 


352  COPPER  SULPHATE. 

Mix  the  ingredients  in  a  flask  and  heat  at  first  gently,  and  after- 
wards raise  the  temperature  gradually  to  the  boiling  point.  Boil 
until  the  evolution  of  gas  ceases,  evaporate  the  solution  to  dryness, 
dissolve  the  residue  in  four  times  its  weight  of  water,  filter  and 
evaporate  to  crystallization.  Dry  the  crystals  without  the  aid  of 
heat. 

Reaction.  3Cua+6H2SO4+4HNO8=6CuSO4+2N2O2+8H2O. 

Granulated  copper  sulphate.  Sulphate  of  copper,  reduced  to 
coarse  powder,  is  dissolved  in  an  equal  weight  of  boiling  water, 
and  the  solution  filtered  and  evaporated  during  constant  stirring 
until  nearly  dry,  after  which  the  residue  is  dried  by  spreading  it  in 
thin  layers  on  paper  and  exposing  it  to  currents  of  dry  air. 

Precipitated  copper  sulphate  may  be  made  by  dissolving  the  salt 
in  its  own  weight  of  boiling  water,  and  filtering  the  solution  into 
an  equal  volume  of  alcohol. 

Turbidated  copper  sulphate  may  be  made  by  dissolving  20  parts 
of  coarsely  powdered  copper  sulphate  in  20  parts  of  boiling  water, 
acidifying  with  I  part  of  diluted  sulphuric  acid,  filtering  the  solu- 
tion while  hot,  and  stirring  the  filtrate  briskly  until  cold.  The 
granular  salt  thus  obtained  is  collected  on  a  filter,  drained,  dried 
at  the  ordinary  temperature,  and  bottled.  The  mother  liquor  is 
evaporated  to  one-half  its  weight  and  an  additional  amount  of 
product  obtained  from  it  in  the  same  manner.  All  of  the  remain- 
ing salt  may  be  recovered  by  evaporation  nearly  to  dryness,  and 
finishing  the  drying  by  exposure  to  the  air. 

Purification  of  Commercial  Blue  Vitriol  may  be  effected  as 
follows : 

Put  the  bluestone  or  blue  vitriol  into  a  porcelain  dish.  Add  3 
parts  of  water.  Apply  heat  and  bring  the  solution  to  the  boiling 
point.  Then  add  small  quantities  at  a  time  of  nitric  acid,  stir  well, 
and  continue  heating.  When  the  liquid  no  longer  gives  off  nitrous 
vapors  on  the  further  addition  of  nitric  acid,  boil  it  a  few  minutes 
longer,  and  then  let  it  cool.  Add  to  the  cold  solution  enough 
water  of  ammonia  to  impart  a  permanent  ammoniacal  odor  to  it. 
Let  it  stand  a  few  hours.  Filter.  Evaporate  to  dryness,  and  heat 
the  residue  strongly  until  it  becomes  nearly  white.  Then  let  it 
cool,  dissolve  it  in  2.5  parts  of  water,  filter  the  solution,  add  o.i 


COPPER  SULPHATE.  353 

part  of  diluted  sulphuric  acid,  mix  well,  and  set  the  liquid  aside  to 
crystallize  by  the  spontaneous  evaporation  of  the  water. 

Collect,  drain  and  dry  the  crystals,  avoiding  loss  of  any  of  their 
water  of  crystallization. 

Iron  is  removed  by  this  process. 

Description. — Copper  sulphate  consists  of  large,  transparent, 
clear,  deep-blue  crystals;  or  a  blue,  granular,  crystalline,  coarse 
powder  if  granulated,  precipitated  by  alcohol,  or  turbidated.  It  is 
odorless,  and  has  a  nauseous,  strongly  metallic  taste.  Slowly  loses 
its  water  of  crystallization  in  dry  air. 

Soluble,  at  15°  C.,  in  about  2.6  parts  of  water,  and  in  0.5  part  of 
boiling  water ;  almost  insoluble  in  alcohol. 

When  carefully  and  continuously  heated  to  30°  C.,  the  salt  loses 
2  of  its  5  molecules  of  water  (14.43  Per  cent),  and  is  converted 
into  a  pale-blue,  amorphous  powder.  Two  more  molecules  of 
water  are  lost  at  100°  C.,  while  the  fifth  is  retained  until  200°  C. 
is  reached,  when  a  white,  anhydrous  powder  remains  (63.9  per 
cent  of  the  original  weight).  At  a  still  higher  temperature  sul- 
phur dioxide  and  oxygen  are  given  off,  and  a  residue  of  black 
cupric  oxide  is  left. 

The  aqueous  solution  (i  in  20)  has  a  blue  color  and  shows  an 
acid  reaction  on  litmus  paper. 


AMMONIATED  COPPER. 

CUPRUM  AMMONIATUM. 

Copper  sulphate 3  parts 

Ammonium  carbonate    4  parts 

Crush  the  salts ;  triturate  them  together  in  a  porcelain  mortar. 

Notes.  The  reaction  between  the  salts  causes  the  mixture  to 
become  wetted  by  the  water  of  crystallization  liberated  from  the 
decomposed  copper  sulphate.  The  mixture  acquires  a  deep-blue 
color.  An  "ammoniacal"  copper  sulphate  is  formed,  the  composi- 
tion of  which  is  uncertain.  Effervescence  takes  place  from  the 
separation  of  CCX. 

\Yhen  effervescence  has  ceased  and  the  mixture  has  been  re- 

Vol.    11-23 


354  AMMONIUM    COPPER  SULPHATE. 

duced  to  a  dry  powder  this  product  is  to  be  kept  in  a  tightly  stop- 
pered bottle. 

This  preparation  is  nearly  similar  in  composition  to  the  crystal- 
line ammoniacal  copper  sulphate,  which  is  more  uniform,  of  hand- 
some appearance,  and  prepared  as  follows  : 

Ammoniacal  Copper  Sulphate. 

Copper  sulphate,  in  powder 10  Gm 

Ammonia  water 30  ml 

Alcohol  of  85%  strength 60  ml 

Dissolve  the  sulphate  of  copper  in  the  ammonia  water  contained 
in  a  porcelain  capsule,  without  applying  heat.  (Heat  is  generated 
by  the  chemical  solution.)  When  the  liquid  has  become  cold, 
filter  it.  Put  the  alcohol  in  a  tall,  narrow  cylinder.  Then  run  in 
under  the  alcohol  10  ml  of  water  by  means  of  a  funnel  tube  reach- 
ing to  the  bottom  of  the  cylinder.  Finally  add  the  copper  solution 
through  the  same  tube  so  that  it  may  form  a  separate  layer  under 
the  water.  Set  it  aside,  without  disturbing  it,  and  well  corked,  for 
one  to  four  weeks,  and  then  decant  the  mother  liquor,  and  throw 
it  away.  Collect  the  crystals  and  dry  them  as  rapidly  as  possible 
without  the  aid  of  heat  by  gently  pressing  them  between  bibulous 
paper,  avoiding  exposure  to  the  air  as  far  as  practicable.  Put  the 
product  at  once  into  a  bottle  and  cork  it  tightly. 

Description. — The  preparation  is  in  handsome,  dark-blue, 
needle-like  crystals,  having  an  ammoniacal  odor  and  a  nauseous, 
metallic  taste.  Soluble  in  1.5  parts  of  water. 

It  is  not  "ammonio-copper  sulphate,"  which  may  be  made  by 
mixing  solutions  of  the  sulphates  of  ammonium  and  of  copper. 

Ammoniacal  copper  sulphate  readily  absorbs  oxygen  from  the 
air,  and  hence  acts  as  an  oxidizing  agent  on  substances  present  in 
its  solution.  Thus,  sodium  thiosulphate  is  rapidly  converted  into 
sulphate;  asparagin  and  glycocoll  to  oxalic  and  carbonic  acids, 
etc. 

Copper  Potassium  Sulphate. 

Copper  sulphate 100  parts 

Potassium  sulphate 70  parts 

Concentrated  sulphuric  acid 12  parts 

Water. 


GOLD.  355 

Dissolve  the  copper  sulphate  in  150  parts  of  hot  water,  and  the 
potassium  sulphate  in  a  similar  quantity  of  hot  water,  to  which 
the  sulphuric  acid  has  been  added.  Mix  the  solutions.  Let  the 
mixture  stand  until  cold.  Collect  the  light-blue  crystals  and  dry 
them.  Evaporate  the  mother-liquor  to  one-half  and  let  cool  again 
to  obtain  a  second  crop. 

Aluminated   Copper. 
(Lapis  Divinus.    Cuprum  Aluminatum.) 

.     Copper  sulphate  ......................    15  parts 

Alum  ...............................    15  parts 

Potassium  nitrate   ....................    15  parts 

Camphor  .............................      i  part 

Powder  the  salts  and  mix  them.  Fuse  the  mixed  powder  in  a 
porcelain  dish,  stirring  well.  Let  the  mass  cool.  Powder  it. 
Finally  add  the  camphor  and  mix  the  whole  intimately  by  tritura- 
tion. 

GOLD;   PURE. 

AURUM    PURUM. 


Gold,  in  coin  or  scraps  ................  12  parts 

Hydrochloric  acid  (38.67%  of  HC1)  .....  32  parts 

Nitric  acid  (68%  of  HNO3)  ...........  7  parts 

Ferrous  sulphate  .....................  55  parts 

Distilled  water. 

Put  the  gold  in  a  flask  with  the  hydrochloric  acid.  Apply  gentle 
heat.  Add  the  nitric  acid,  a  little  at  a  time,  until  the  metal  is  com- 
pletely dissolved  (leaving  only  the  precipitated  silver  chloride 
formed  by  the  silver  contained  in  the  gold  coin  or  scraps,  if  al- 
loyed with  silver).  Filter  the  solution  through  -a  paper  filter, 
washing  the  silver  chloride  on  the  filter  with  a  little  distilled  water 
and  adding  the  washings  to  the  filtrate.  Evaporate  the  filtrate  to 
a  syrupy  consistence,  weigh  it,  and  dilute  it  with  ten  times  its 
weight  of  distilled  water. 

Dissolve  the  ferrous  sulphate  in  250  parts  of  distilled  water, 


356  GOLD. 

acidulate  the  solution  with  5  parts  of  diluted  hydrochloric  acid, 
heat  to  boiling,  filter,  and  let  the  filtrate  cool. 

Add  the  solution  of  ferrous  sulphate  very  gradually  and  with 
constant  stirring  to  the  solution  of  gold  chloride.  Set  the  mix- 
ture in  a  warm  place  for  an  hour.  Then  collect  the  yellowish- 
brown  precipitate  of  metallic  gold  upon  a  paper  filter,  wash  it  first 
with  a  little  diluted  hydrochloric  and  afterwards  with  distilled 
water.  Dry  the  product  with  the  aid  of  moderate  heat. 

Reactions.  First,  2Au+3d2— 2AuQ3 ;  then,  2AuQ3+6FeSO4 
=2Au+2Fe2  ( S04)  3+Fe2Cl6. 

Notes.  Coin  gold  and  gold  employed  in  making  jewelry  and 
gold  vessels  is  alloyed  with  either  silver  or  copper,  or  both.  The 
silver  forms  insoluble  silver  chloride  when  the  gold  coin  is  dis- 
solved in  the  hydrochloric  and  nitric  acids.  [This  silver  chloride 
should  be  collected  and  may  be  reduced  to  metallic  silver,  when 
convenient,  as  described  under  the  title  of  Silver;  Pure]  Cop- 
per dissolves  together  with  the  gold,  but  remains  in  the  liquid 
when  the  gold  is  precipitated  with  ferrous  sulphate. 

The  solution  of  gold  chloride  and  that  of  ferrous  sulphate 
should  be  perfectly  clear  when  about  to  be  mixed.  Ferrous  chlor- 
ide may  be  used  in  place  of  ferrous  sulphate. 

The  precipitated  gold  is  chemically  pure  and  so  finely  divided 
that  it  is  easily  dissolved  in  hydrochloric  and  nitric  acids  mixed 
together. 

Oxalic  acid  (pure)  may  be  used  instead  of  ferrous  sulphate  for 
the  precipitation  of  the  gold. 

2AuCl3+3H2C2O4=2Au+6HCl+6CO2. 

The  amount  of  crystallized  oxalic  acid  required  for  12  parts  of 
gold  is  about  12.5  parts. 

GOLD  CHLORIDE. 

AURI    CHLORIDUM. 
AuCl3=302.8. 

Pure  gold 10  parts 

Hydrochloric  acid  (38.67%  HC1) 26  parts 

Nitric  acid  (68%  HNO3) 7  parts 


GOLD  CHLORIDE.  357 

Mix  the  acids.  Dissolve  the  gold  in  the  mixture  with  the 
aid  of  gentle  heat.  Evaporate  the  solution  to  dryness.  Fuse  it  at 
a  temperature  not  exceeding  150°. 

Put  the  dry  salt  in  a  perfectly  dry  glass-stoppered  bottle  and 
keep  it  in  a  cool,  dark  place. 

Notes.  The  amount  of  nitric  acid  prescribed  here  is  probably 
just  sufficient.  More  is  usually  ordered.  An  excess  should  not  be 
used.  Gold  chloride  is  unstable;  it  keeps  better  if  mixed  with 
sodium  chloride.  The  pharmacopoeias  generally  prescribe  a  mix- 
ture of  equal  parts  of  gold  chloride  and  sodium  chloride,  but  some 
pharmacopoeias  prescribe  a  smaller  proportion  of  the  sodium 
chloride. 

Description. — Golden  yellow,  transparent  crystals;  odorless; 
taste  metallic.  Deliquescent  in  moist  air. 

Chloride  of  Gold  with  Sodium  Chloride. 

Pure  gold 10     parts 

Pure  sodium  chloride 15.4  parts 

Hydrochloric  acid  of  38.67%  strength.  .   26      parts 
Nitric  acid  of  68%  to  70%  strength,  sufficient. 

Mix  the  hydrochloric  acid  with  6  parts  of  the  nitric  acid.  Add 
the  gold.  Let  the  gold  dissolve,  adding  more  nitric  acid  later  on, 
if  necessary,  to  effect  the  solution  of  the  gold,  but  taking  care  not 
to  add  more  than  is  necessary.  Apply  gentle  heat  to  facilitate  the 
solution.  When  all  of  the  gold  has  been  dissolved  evaporate  the 
solution  to  dryness  and  fuse  the  residue  at  as  low  a  temperature  as 
possible,  not  exceeding  150°.  Then  redissolve  the  gold  chloride 
in  30  parts  of  distilled  water,  dissolve  the  sodium  chloride  in  the 
gold  solution,  then  evaporate  to  dryness,  and  reduce  the  product 
to  coarse  powder.  Keep  it  in  a  glass-stoppered  bottle. 

Keep  the  product  in  a  dark  place. 

Notes.  The  gold  chloride  obtained  by  dissolving  gold  in  nitro- 
hydrochloric  acid  and  evaporating  the  solution  to  dryness  without 
subsequently  fusing  the  salt  is  a  mixture  of  aurochloric  acid 
(HAuCl4.2H2O)  and  gold  trichloride.  The  unusually  strong  hy- 
drochloric acid  ordered  in  these  formulas  is. preferable  to  the  offi- 
cial acid.  A  hydrochloric  acid  of  38.67%  strength  has  the  sp.  w. 
of  about  1.19. 


358  GOLD  CHLORIDE. 

The  pure  gold  required  is  precipitated  as  described  under 
Gold. 

Description. — The  gold  and  sodium  chloride  of  the  American 
Pharmacopoeia  consists  of  equal  weights  of  gold  trichloride  and 
sodium  chloride.  It  is  a  coarse,  orange  yellow,  granular  powder ; 
odorless ;  taste  saline,  metallic.  It  is  slightly  deliquescent  in  moist 
air.  Readily  soluble  in  water.  Alcohol  dissolves  the  gold  chloride, 
leaving  the  sodium  chloride,  which  should  constitute  not  more 
than  one-half  by  weight  of  the  whole  quantity  added  to  the  alco- 
hol. 

Another  Method. 

This  preparation  may  be  made  as  follows : 

Pure  gold 13  parts 

Hydrochloric  acid   (32%) 37.5  parts 

Nitric  acid  (68% ) 6  parts 

Distilled  water   40  parts 

Dry  pure  sodium  chloride 20  parts 

Dissolve  the  gold  in  the  mixed  acids.  Add  the  water.  Dis- 
solve the  sodium  chloride  in  the  liquid.  Evaporate  the  liquid  over 
a  water-bath  to  dryness. 

Notes.  In  this  formula,  which  is  constructed  after  that  of  the 
German  pharmacopoeia,  there  is  rather  more  hydrochloric  acid  and 
less  nitric  acid  prescribed  than  in  other  working  formulas. 

Another  Method. 

(After  the  Swiss  Pharmacopoeia.) 

Pure  gold 65  parts 

Hydrochloric  acid  (25%  of  HC1) 180  parts 

Nitric  acid  (32.3%  of  HNO3,  or  1.2  sp.  w) .  .  60  parts 

Sodium  chloride 100  parts 

Distilled   water    100  parts 

Mix  the  acids.  Dissolve  the  gold  in  the  mixture  with  the  aid 
of  gentle  heat.  Evaporate  the  solution  over  a  water-bath  to  the 
consistence  of  syrup,  so  that  upon  cooling  it  forms  a  solid  salt 
mass.  Dissolve  this  gold  chloride  in  the  distilled  water,  add  the 
completely  dried  (decrepitated)  sodium  chloride,  and  evaporate 
to  dryness  over  a  water-bath. 


HYDROGEN.  359 

HYDROGEN. 


Hydrogen  gas,  when  required  for  laboratory  operations,  may  be 
made  as  follows  : 

Zinc  granulated  .....................     70  parts 

Sulphuric  acid  ......................    100  parts 

Water    ............................  .   500  parts 

Put  the  zinc  in  a  wide-mouthed  half-gallon  bottle  provided  with 
a  twice  perforated  rubber  stopper,  fitted  with  thistle-tube  and  a 
bent  delivery  tube.  Connect  the  delivery  tube  with  a  wash-bottle 
of  about  a  quart's  capacity  containing  a  pint  of  water,  and  provide 
the  wash  bottle  with  the  necessary  delivery  tube,  which  may  be, 
in  turn,  connected  with  any  bottle  or  tube  into  which  the  hydrogen 
is  to  be  conducted. 

Add  the  sulphuric  acid  to  the  zinc  through  the  thistle  tube,  as 
required. 

The  most  convenient  apparatus  for  producing  hydrogen,  as  well 
as  hydrogen  sulphide  and  several  other  gases,  is  Kipp's  apparatus. 

Reaction.    Zn+H2SO4=ZnSO4+-H2. 

Sixty-five  Gm  of  zinc,  if  all  consumed,  will  furnish  2,  Gm  of 
hydrogen  according  to  this  equation.  One  cubic-decimeter  of 
hydrogen  at  o°  C.,  bar.  760  mm.,  weighs  about  0.09  Gm,  and  2.  Gm 
of  hydrogen,  therefore,  occupies  about  11.16  cubic-decimeters. 


HYDROGEN  DIOXIDE  SOLUTION. 

LIQUOR    HYDROGEN  1  1    DIOXIDI. 

A  water-solution  containing,  when  fresh,  about  3  per  cent  of 
hydrogen  dioxide,  H2O2,  corresponding  to  about  10  volume  units 
of  free  oxygen  obtainable  from  each  volume  unit  of  the  solution. 

Apparatus  required  for  the  preparation  of  about  i  liter:  Two 
half  -gallon  bottles.  White  paper  filters  of  30  Cm  diameter  and 
of  such  character  as  to  admit  of  rapid  filtration.  A  funnel  to 
correspond  to  the  size  of  the  filter. 


360  HYDROGEN  DIOXIDE. 

Materials.  Barium  dioxide,  .300  Gm;  phosphoric  acid  (85%), 
about  100  ml;  diluted  sulphuric  acid,  about  2  ml;  starch,  in  pow- 
der, about  10  Gm;  distilled  water,  about  I  liter. 

Process.  Put  500  ml  of  cold  distilled  water  into  a  half-gallon 
bottle.  Add  gradually  the  coarse  powder  of  the  barium  dioxide, 
and  shake  after  each  addition  to  break  up  any  lumps  that  might 
be  formed.  When  all  of  the  barium  dioxide  has  been  added  shake 
the  bottle  vigorously  so  that  the  contents  may  form  a  uniform 
mixture. 

Place  the  bottle  in  a  vessel  of  water  cooled  by  additions  of 
broken  ice  so  that  the  contents  may  be  kept  at  a  temperature 
somewhat  below  10°  C.  (50°  F.)  for  about  half  an  hour.  During 
that  time  shake  the  bottle  thoroughly  every  few  minutes.  Con- 
tinue keeping  the  mixture  cool  and  shaking  it  occasionally  and 
strongly  until  the  barium  dioxide  shall  have  been  converted  into 
hydroxide,  which  may  be  known  by  the  fact  that  but  little  water 
is  separated  on  standing  and  that  a  uniform  mixture  may  be 
obtained,  without  difficulty,'  by  shaking. 

Put  into  the  other  half-gallon  bottle  96  ml  of  phosphoric  acid 
and  320  ml  of  distilled  water,  and  cool  this  mixture  to  about 
10°  C.  Take  of  this  liquid  50  ml  and  set  that  aside.  To  the 
remainder  of  the  mixture  of  phosphoric  acid  and  water  add,  in 
four  equal  portions,  the  well-mixed  magma  from  the  first  bottle, 
shaking  the  mixture  vigorously  and  cooling  it  after  each  addi- 
tion. Note  the  reaction  of  the  mixture  upon  litmus  paper,  and, 
when  it  shows  an  alkaline  reaction,  add  cautiously  enough  of  the 
reserved  dilute  phosphoric  acid  to  render  the  reaction  again  acid. 

Repeat  the  vigorous  shaking  of  the  bottle  and  the  gradual 
addition  of  more  phosphoric  acid  until  the  liquid  no  longer  be- 
comes alkaline  upon  long  continued  strong  shaking.  (Should 
the  reserved  portion  of  the  mixture  of  phosphoric  acid  and  water 
prove  insufficient  to  effect  a  slightly  acid  reaction,  mix  a  sufficient 
additional  amount  of  phosphoric  acid  and  distilled  water  in  the 
same  proportions  as  before,  and  add  of  this  as  much  as  may  be 
necessary.) 

When  the  whole  mixture  shall  have  been  finally  thoroughly 
shaken  until  the  liquid  portion  has  acquired  a  neutral  reaction  on 
test  paper,  set  the  bottle  aside  and  let  it  rest  until  the  supernatant 
liquid  occupies  abou^  two-thirds  of  the  volume  of  the  whole  mix- 


HYDROGEN  DIOXIDE.  361 

ture.  Then  decant  that  liquid  upon  a  wetted  double  filter  of 
white  filter  paper  about  30  Cm  in  diameter.  When  the  liquid 
has  passed  through  the  filter,  transfer  the  thick  mixture  con- 
taining the  precipitate  to  the  same  filter.  Rinse  the  bottle  with 
100  ml  of  distilled  water  and  pour  this  also  upon  the  filter.  Wash 
the  precipitate  on  the  filter  with  more  distilled  water  collecting 
the  washings  in  the  previous  filtrate  until  the  total  quantity  of 
filtered  liquid  measures  i  liter. 

Add  to  this  filtrate  20  drops  of  diluted  sulphuric  acid  and  shake 
well.  Filter  a  small  portion  of  the  liquid,  and  add  to  this  clear 
sample  a  few  drops  of  diluted  sulphuric  acid  again.  Should  this 
render  the  clear  solution  cloudy,  continue  to  add  small  quantities 
of  diluted  sulphuric  acid  until  a  further  addition  of  it  no  longer 
produces  cloudiness  in  a  filtered  sample.  (The  filtration  of  the 
test  samples  may  be  rendered  more  effective  by  the  addition  of 
a  little  starch.) 

Add  to  the  whole  liquid  about  10  Gm  of  starch  and  shake  the 
mixture  thoroughly.  Filter  the  liquid  through  a  wetted  white 
paper  filter  of  the  same  size  as  before,  returning  to  the  filter  the 
first  portions  of  the  filtrate,  until  a  clear  liquid  passes  through. 

Assay  the  filtrate  by  the  method  given  below  and  dilute  it  with 
distilled  water  so  that  the  final  product  shall  contain  3  per  cent 
of  absolute  hydrogen  dioxide. 

Assay  process.  Dilute  10  ml  of  the  solution  with  90  ml  of  dis- 
tilled water.  Put  17  ml  of  the  liquid  in  a  beaker,  add  5  ml  of 
diluted  sulphuric  acid,  and  then  run  into  the  mixture,  from  a 
burette,  a  sufficient  quantity  of  decinormal  volumetric  solution 
of  potassium  permanganate  to  impart  a  faint  pink  tint  which  does 
not  at  once  disappear  on  stirring.  Each  ml  of  the  volumetric 
solution  required  corresponds  to  0.0017  Gm  of  H2O2. 

The  number  of  ml  of  permanganate  solution  decolorized  by 
each  1.7  ml  of  the  solution  of  hydrogen  dioxide  multiplied  by  0.33 
gives  a  product  expressing  the  number  of  volumes  of  oxygen 
yielded  by  one  volume  of  its  solution. 

The  number  of  ml  of  permanganate  solution  decolorized  by  each 
1.7  ml  of  solution  of  hydrogen  dioxide  divided  by  10  gives  a 
quotient  expressing  the  per  cent  by  weight  of  H2O2  contained 
in  the  solution. 

Instead  of  taking  1.7  ml  of  the  solution  for  the  valuation  (17 


362  HYDROGEN  DIOXIDE. 

ml  of  the  diluted  solution),  i  ml  may  be  taken  (using  10  ml  of 
a  mixture  made  of  10  ml  of  the  solution  and  90  ml  of  distilled 
water).  The  number  of  ml  of  permanganate  solution  decolorized 
by  each  ml  of  the  solution  of  hydrogen  dioxide  when  multiplied 
by  0.56  gives  a  product  expressing  the  number  of  volumes  of 
oxygen  yielded  by  one  volume  of  the  solution  of  H2O2.  The 
number  of  ml  of  permanganate  solution  decolorized  by  each  ml  of 
solution  of  hydrogen  dioxide  when  multiplied  by  0.17  gives  a 
product  expressing  the  per  cent  of  H2O2  contained  in  the  prepara- 
tion. Each  1.7  ml  of  the  solution  of  H2O2  should  require  not 
less  than  30  ml  of  the  volumetric  permanganate  solution,  or  each 
ml  should  require  not  less  than  17.65  ml.  The  reaction  which 
takes  place  in  the  assay  process  is : 

5H2O2+3H2SO4+2KMnO4=K2SO4+2MnSO4+8H2O+5O2. 

Thus  2,  molecules  of  KMnO4  are  required  for  5  molecules  of 
H2O2.  As  the  mol.  weight  of  KMnO4  is  158  and  that  of  H2O2 
is  34,  and  as  the  permanganate  solution  is  a  decinormal  one 
it  follows  that  each  ml  of  the  volumetric  solution,  containing 
0.00316  Gm  of  KMnO4  corresponds  to  0.0017  Gm  of  H2O2  or  to 
0.0008  Gm  of  available  O2. 

Notes.  The  first  reaction  by  which  the  barium  dioxide  is  de- 
composed is  : 

BaO2+2H2O=Ba(OH)2+H2O2. 

The  completion  of  this  reaction  is  facilitated  by  cooling  the 
water  below  10°  C,  and  may  be  known  to  have  been  attained 
when  a  magma  has  been  formed  from  which  but  little  water 
separates  on  standing. 

The  barium  is  then  precipitated  by  means  of  phosphoric  acid. 
3Ba  (OH)  2+2H,PO4=Ba3  ( PO4)  2+6H2O. 

If  necessary  a  little  sulphuric  acid  may  be  used,  as  directed  by 
the  Pharmacopoeia,  to  complete  the  separation  of  the  barium. 

All  that  then  remains  to  be  done  is  the  filtration  of  the  liquid 
and  the  adjustment  of  its  strength  to  the  prescribed  standard. 


HYDROGEN  DIOXIDE.  363 

The  filtration  is  frequently  difficult.  A  double  filter  is  neces- 
sary and  starch  is  added  to  further  aid  the  clarification. 

Small  quantities  of  phosphoric  and  sulphuric  acids  are  un- 
avoidably left  in  the  product,  and  their  presence  tends  to  pre- 
serve it. 

Hydrogen  dioxide  is  very  unstable,  and  its  uses  depend  upon 
that  fact ;  it  decomposes  into  water  and  oxygen.  Heat  and  light 
hasten  this  decomposition.  Hence  it  must  be  kept  in  a  cool  place 
and  protected  from  light.  But  it  can  not  be  kept  in  tightly  stop- 
pered bottles  because  the  containers  would  burst  should  the 
dioxide  decompose  in  them. 

Solution  of  hydrogen  dioxide  may  be  evaporated  on  a  water- 
bath,  at  a  temperature  not  exceeding  60°  C.,  until  reduced  to  one- 
fifth  of  its  original  volume,  being  thus  rendered  five  times  the 
official  strength,  or  made  of  such  strength  that  each  volume  of 
the  concentrated  solution  will  yield  fifty  volumes  of  oxygen  upon 
decomposition  of  the  hydrogen  dioxide  it  contains. 

One  per  cent  of  boroglycerin  is  said  to  retard  the  decomposi- 
tion of  the  solution.  It  should  be  kept  in  a  cool,  dark  place. 

Description. — A  colorless,  odorless  liquid,  slightly  acidulous  in 
taste  and  producing  a  peculiar  sensation  and  soapy  froth  in  the 
mouth.  Reaction  acid,  owing  to  the  free  acid  left  in  the  liquid 
to  preserve  it.  The  dioxide  is  liable  to  decomposition  when  the 
solution  is  rapidly  heated  to  a  temperature  above  60°  C. 


HYDROGEN  SULPHIDE. 

H2S=34. 

When  hydrogen  sulphide  is  required  for  laboratory  operations, 
as  in  the  preparation  of  hydrobromic  or  hydriodic  acid,  it  may 
be  produced  as  follows : 

Put  any  convenient  and  suitable  quantity  of  ferrous  sulphide 
in  small  fragments  into  a  Kipp's  apparatus  (Fig.  — )  and  add 
diluted  sulphuric  acid,  or  diluted  hydrochloric  acid,  as  required. 
The  ferrous  sulphide  is  first  covered  with  water  in  the  apparatus, 
and  the  dilute  acid  then  added  as  may  be  necessary. 


364  IODINE. 

IODINE. 

IODUM. 
1=126.5. 

Commercial  iodine  is  easily  resublimed.  Small  quantities  may 
be  resublimed  in  a  dish  heated  in  a  sand-bath  the  sublimate  being 
collected  in  an  inverted  funnel  which  is  placed  over  the  contents 
of  the  dish. 

Resublimed  or  purified  iodine  consists  of  dry,  brittle,  shining 
purplish-black  crystals  of  a  strong  characteristic  odor  and  acrid 
taste.  Soluble  in  alcohol. 

Iodine  imparts  yellowish-brown  or  deep  brown  stains  to  thfe 
skin  and  to  articles  with  which  it  comes  in  contact.  The  stains  and 
odor  are  persistent.  Mortars  and  other  apparatus  stained  with 
iodine  may  be  cleaned  with  potassium  or  sodium  hydroxide,  am- 
monia, potassium  iodide  or  sodium  thiosulphate ;  but  the  stains 
on  the  hands  and  organic  substances  generally  can  not  be  thus 
removed. 

Iodine  must  be  kept  in  glass-stoppered  bottles. 

Compound  Iodine  Solution. 
(LUGOI/S    SOLUTION.) 

Dissolve  5  Gm  of  iodine  and  10  Gm  of  potassium  iodide  in  85 
Gm  of  distilled  water. 

Keep  the  solution  in  a  glass-stoppered  bottle. 

Description. — A  deep-red  solution  of  strong  iodine  odor. 
Tincture  of  Iodine,  U.  S.  P. 

Reduce  70  Gm  of  iodine  to  coarse  powder  by  trituration  in  a 
mortar.  Transfer  it  to  a  graduated  glass-stoppered  bottle  of 
about  one  and  one-half  liters'  capacity.  Rinse  the  mortar  with 
several  successive  portions  of  alcohol,  and  pour  these  washings 
into  the  bottle.  Add  enough  additional  alcohol  to  make  the  total 
volume  of  the  contents  of  the  bottle  measure  one  liter.  Set  the 
bottle  in  a  warm  place.  Agitate  it  occasionally  until  the  iodine 
is  dissolved. 


IODINE.  365 

Notes.  The  official  tincture  of  iodine  is  so  nearly  a  saturated 
solution  at  ordinary  low  room  temperature  that  it  would  be  un- 
wise to  increase  its  strength  to  10  per  cent,  which  is  the  stand- 
ard of  some  pharmacopoeias.  The  solution  takes  place  so  slowly 
that  it  is  best  to  powder  the  iodine  and  to  put  the  mixture  in  a 
warm  place  to  reduce  the  time  required  for  its  completion. 

Description. — A  deep  red  solution  of  strong  iodine  odor.  But 
the  peculiar  odor  of  an  old  tincture  of  iodine  indicates  that  it  con- 
tains not  only  iodine  and  alcohol  but  also  small  quantities  of  some 
products  formed  by  interaction  between  them. 

Decolorised  Tincture  of  Iodine. 

Iodine    4  Gm 

Alcohol    40  ml 

Stronger  water  of  ammonia 9  ml 

Powder  the  iodine  by  trituration.  Dissolve  it  in  the  alcohol. 
Add  the  ammonia  water  carefully  without  shaking  or  stirring  the 
mixture. 

Let  the  mixture  stand  exposed  to  sunlight  until  decolorized, 
which  will  require  from  a  few  days  to  several  weeks. 

Notes.  As  explosive  nitrogen  iodide  is  liable  to  be  produced 
when  the  ammonia  is  added  to  the  iodine  solution,  any  dark- 
colored  sediment  formed  in  the  liquid  should  warn  the  operator 
to  leave  the  mixture  at  perfect  rest  until  the  precipitate  has  dis- 
appeared, which  it  will  finally  do.  If  a  few  drops  of  phenol  be 
added  to  the  mixture  it  becomes  decolorized  at  once  on  shaking. 

The  preparation  contains  not  iodine,  but  ammonium  iodide  and 
ethyl  iodide. 

Another  Formula. 

Iodine    10  parts 

Sodium  thiosulphate 10  parts 

Ammonia    water 15  parts 

Alcohol    75  parts 

Distilled  water,  sufficient. 

Dissolve  the  iodine  and  the  sodium  thiosulphate  in  10  parts 
of  distilled  water;  add  the  ammonia  water,  and,  finally,  the 
alcohol.  Let  the  mixture  stand  three  days,  and  then  filter. 


366  IRON. 

Notes.     This  preparation  contains  sodium  iodide,  ammonium 
iodide,  ethyl  iodide,  sodium  tetrathionate,  alcohol  and  water. 


IRON. 

FERRUM. 

Powdered  Iron. 

Metallic  iron  prepared  by  riling  the  metal  and  triturating  the 
filings  in  steel  mortars.  The  iron  used  for  this  purpose  may  be 
either  cast  iron,  wrought  iron,  or  steel.  Wrought  iron  is,  however, 
extremely  difficult  to  powder,  and  cast  iron  contains  rather  too 
much  carbon. 

Description  and  Tests.  — A  heavy,  gray,  impalpable  powder. 

Soluble  in  dilute  hydrochloric  acid  without  residue  except  traces 
of  carbon.  The  gas  evolved  when  it  is  dissolved  in  HC1  should 
have  no  odor  of  H2S  (absence  of  sulphur).  The  solution 
oxidized  with  nitric  acid  and  completely  precipitated  with  am- 
monia should  not  yield  a  blue  liquid  (absence  of  copper).  It 
should  be  free  from  arsenic. 

Uses.  Powdered  iron  ("ferrum  pulveratum")  is  used  in  medi- 
cine in  the  same  way  as  "reduced  iron." 

Reduced   Iron. 

Prepared  by  reducing  basic  ferric  hydroxide  or  ferric  oxide 
to  metallic  iron  by  means  of  hydrogen,  at  a  sufficiently  high  heat. 

Ferric  hydroxide  is  prepared  by  precipitation  from  a  solution  of 
ferric  sulphate  by  means  of  ammonia  in  the  usual  way,  and  the 
thoroughly  washed  precipitate  is  dried.  This  dried  ferric  hydrox- 
ide is  introduced  into  an  iron  tube  and  confined  to  the  middle  of 
that  tube  by  means  of  asbestos  plugs.  The  tube  is  placed  in  a 
furnace  and  the  middle  portion  of  it,  containing  the  basic  ferric 
hydroxide,  is  heated  to  "a  strong  but  not  bright  red"  heat.  Then 
hydrogen,  obtained  by  the  action  of  zinc  on  sulphuric  acid,  is 
passed  through  the  tube.  The  hydrogen  gas,  before  it  is  passed 
through  the  reduction  tube,  is  dried  by  passing  it  through  strong 
sulphuric  acid  and  then  through  "a  tube  eighteen  inches  long" 
filled  with  fragments  of  calcium  chloride.  "The  farther  end  of  the 


IRON.  367 

iron  tube  is  connected  by  a  cork  with  a  bent  tube  dipping  under 
water;  and  when  the  hydrogen  is  observed  to  pass  through  the 
water  at  about  the  rate  that  it  bubbles  through  the  sulphuric  acid, 
the  furnace  is  to  be  allowed  to  cool  down  to  the  temperature  of 
the  atmosphere,  a  slow  current  of  hydrogen  being  still  continued." 
Reduced  iron  must  be  kept  in  small,  dry,  tightly-stoppered 
bottles. 

Reaction.     Fe2O3+3H2=2Fe+3H2O. 

Notes.  The  thoroughly  dried  ferric  hydroxide  (it  is  rendered 
partly  basic  in  drying,  and  soon  becomes  entirely  converted  into 
ferric  oxide  when  heated)  must  be  in  fine  powder.  This  is  placed 
in  an  iron  tube  (such  as  a  gun  barrel,  or  a  tube  constructed  ex- 
pressly for  this  operation).  Hydrogen  is  then  passed  through 
the  tube  over  the  basic  ferric  hydroxide.  The  hydrogen  must  be 
pure  and  is  therefore  passed  through  solution  of  lead  acetate  to 
remove  sulphur,  through  copper  sulphate  or  silver  nitrate  solution 
to  remove  arsenic  and  phosphorus,  and  through  concentrated  sul- 
phuric acid  to  remove  moisture,  before  it  enters  the  iron  tube. 
When  the  gas  has  passed  over  the  ferric  hydroxide  for  a  minute 
so  that  the  tube  is  filled  with  the  gas,  heat  is  applied  at  the  point 
where  the  ferric  hydroxide  is  placed,  and  the  temperature  is  grad- 
ually raised.  At  about  350°  C.  the  ferric  hydroxide  is  reduced 
to  ferroso-ferric  oxide ;  at  about  500°  C.  to  ferrous  oxide ;  and  at 
about  700°  C.  to  metallic  iron.  It  is  necessary,  therefore,  that 
the  temperature  should  be  sufficiently  high,  for  if  the  product 
should  contain  much  ferrous  oxide  it  will  become  self-igniting  in 
contact  with  air.  On  the  other  hand,  if  heated  too  strongly,  the 
iron  particles  cake  together  and  incomplete  reduction  will  be  the 
result.  The  tube  and  its  contents  should,  therefore,  be  heated  ro 
"dull  red  heat" — not  to  a  "bright  red  heat." 

The  heating  must  be  continued  until  the  gas  after  passing 
through  the  tube  no  longer  deposits  moisture  on  a  glass  plate  or 
other  suitable  cold  object  held  near  the  end  of  the  reduction  tube. 
The  reduction  is  then  completed  and  the  heat  is  to  be  withdrawn ; 
but  the  current  of  hydrogen  through  the  tube  must  be  continued 
until  the  tube  and  contents  have  cooled  off,  for  if  the  reduced 
iron,  while  still  hot,  comes  in  contact  with  air,  it  might  ignite  and 
become  oxidized  again. 


368  IRON  ACETATE. 

Description. — A  very  fine,  grayish-black,  lustreless,  odorless 
and  tasteless  powder.  The  Americal  Pharmacopoeia  requires  it 
to  contain  at  least  80  per  cent  of  metallic  iron ;  the  British  Phar- 
macopoeia 75  per  cent. 


IRON  (FERRIC)  ACETATE  SOLUTION. 

LIQUOR    FERRI    ACETATIS. 

An  aqueous  solution  of  ferric  acetate  (Fe(C2H3O2)  3=233) 
containing  about  31  per  cent  of  the  anhydrous  salt,  corresponding' 
to  about  7.5  per  cent  of  iron. 

Solution  of  ferric  sulphate 100  parts 

Glacial  acetic  acid 26  parts 

Ammonia  water 85  parts 

Distilled  water,  sufficient. 

To  the  ammonia  water  diluted  with  300  parts  of  cold  water  add, 
constantly  stirring,  the  solution  of  ferric  sulphate  previously 
diluted  with  1000  parts  of  cold  water.  Pour  the  whole  on  a  wet 
muslin  strainer,  allow  the  precipitate  to  drain,  then  return  it  to 
the  vessel  and  mix  it  intimately  with  600  parts  of  cold  water ; 
again  drain  it  on  the  strainer,  and  repeat  the  washing  with  succes- 
sive portions  of  cold  water  until  the  washings  are  no  longer  af- 
fected by  sodium  cobaltic  nitrate  test-solution  (showing  the 
removal  of  ammonia  and  its  salts).  Transfer  the  mixture  to  a  wet 
muslin  strainer,  allow  the  precipitate  to  drain  completely,  and 
press  it,  folded  in  the  strainer,  until  its  weight  is  reduced  to  70 
parts  or  less  by  expressing  the  water  from  it.  Now  add  the 
pressed  ferric  hydroxide  gradually  to  the  glacial  acetic  acid  in  a 
tared  jar  provided  with  a  glass  stopper,  stirring  the  mixture  after 
each  addition  until  each  portion  added  has  been  nearly  dissolved 
before  another  portion  is  added.  Finally,  when  all  of  the  ferric 
hydroxide  has  been  added,  and  no  more  of  it  dissolves,  add  enough 
distilled  water  to  make  the  product  weigh  100  parts,  mix  well, 
allow  the  mixture  to  become  clear  by  subsidence,  and  decant  the 
clear  solution,  or  draw  it  off  by  means  of  a  syphon. 


IRON   ACETATE.  369 

Solution  of  acetate  of  iron  should  be  kept  in  well  stoppered 
bottles,  protected  from  light,  in  a  cool  place. 

Reaction.    First,  Fe,,(SOJ3+6H4NOH=2Fe(OH)3 

•+3(H4N)2S04; 
then,  Fe(OH)3+3HC2H302=Fe(C2H302)3+3H20. 

Notes.  In  order  to  make  this  preparation  successfully,  the  di- 
rections must  be  strictly  obeyed.  Cold  liquids  must  be  used 
throughout,  and  if  practicable  the  solution  should  be  made  in  cool 
weather.  See  the  notes  on  ferric  hydroxide. 

The  washings  may  be  tested  with  either  barium  chloride  or  so- 
dium cobaltic  nitrate.  When  the  hydrate,  has  been  well  washed  and 
drained,  as  much  as  possible  of  the  water  held  by  the  magma  must 
be  forcibly  pressed  out,  and  the  weight  of  the  hydroxide  thus  re- 
duced to  the  quantity  stated.  This  is  necessary  because  a  larger 
quantity  of  moisture  retained  in  the  magma  would  so  dilute  the 
acetic  acid  that  it  could  no  longer  dissolve  the  hydroxide,  so  that 
a  turbid  mixture  instead  of  a  clear  solution  would  result.  No 
heat  must  be  employed,  because  heat  decomposes  the  ferric  hy- 
droxide, rendering  it  insoluble,  whilst  it  at  the  same  time  vola- 
tilizes acetic  acid.  Even  the  elevation  of  temperature  caused  by 
the  solution  of  the  ferric  hydroxide  in  the  strong  acetic  acid  is 
too  great  not  to  require  to  be  kept  under  control  so  far  as  prac- 
ticable. To  obviate  this  generation  of  heat,  the  ferric  hydroxide 
should  be  added  in  small  portions  at  a  time  to  the  acid,  as  directed. 

Filtration  is  impracticable,  or  perhaps  worse  than  useless.  If 
the  solution  is  unclear,  it  will  be  rendered  more  so  by  any  exposure 
to  the  air  during  nitration,  from  loss  of  acetic  acid,  and  chemical 
changes,  and  even  if  the  filtration  be  carried  out  so  carefully  as 
to  effectually  prevent  loss  of  acid  and  access  of  air,  the  liquid 
will  pass  through  the  filter  paper  extremely  slowly  and  rarely 
clearer  than  before. 

The  preparation  is  used  in  making  tincture  of  acetate  of  iron. 

Several  pharmacopoeias  prescribe  ferric  chloride  instead  of 
ferric  sulphate,  to  produce  the  ferric  hydroxide  with  which  the 
acetic  acid  is  to  foe  saturated. 

The  solution  of  ferric  acetate  of  the  Pharmacopoeia  of  the 
United  States  would  seem  to  be  unnecessarily  strong.  A  solution 

Vol.    11—24 


37O  IRON  ACETATE. 

representing  5  per  cent  of  its  weight  of  metallic  iron  is  more  easily 
obtained  (see  German  formula  below). 

Description. — The  solution  of  acetate  of  iron  of  the  American 
Pharmacopoeia  is  a  dark  brown-red,  clear  liquid  of  acetous  odor, 
sweetish-acidulous,  mildly  styptic  taste,  and  slightly  acid  reaction. 
Sp.  w.  about  1.160  at  15°. 

This  preparation  is  about  50  per  cent  stronger  than  that  of  the 
German  and  Swiss  pharmacopoeias,  both  of  which  contain  a  solu- 
tion corresponding  in  strength  to  from  4.8  to  5  per  cent  of  metallic 
iron,  while  the  American  preparation  contains  about  7.5  per  cent 
of  iron. 

The  "Solution  of  Ferric  Acetate"  of  the  British  Pharmacopoeia 
contains  only  1.65  per  cent  of  metallic  iron.  Thus  1000  parts  by 
weight  of  the  American  solution  equals  4545  parts  of  the  British 
solution  of  the  same  name. 

German  Official  Formula  (Ed.  III). 
[The  Swiss  preparation  is  the  same.] 

Solution  of  ferric  chloride,  U.S.P 20  parts 

Ammonia   water    27  parts 

Acetic  acid,  U.S.P 17  parts 

Distilled  water,  sufficient. 

Dilute  the  solution  of  ferric  chloride  with  125  parts  of  distilled 
water,  and  the  ammonia  water  with  500  parts.  Add  the  iron  solu- 
tion slowly  and  during  constant  stirring  to  the  dilute  ammonia 
solution.  Wash  the  precipitate  in  the  usual  manner  with  cold 
distilled  water.  Let  the  precipitate  drain  and  express  as  much  of 
the  water  from  it  as  possible  by  means  of  strong  pressure. 

Put  the  moist  mass  of  ferric  hydroxide  thus  obtained  into  a 
suitable  vessel  with  the  acetic  acid,  and  set  the  mixture  aside  in  a 
cool  place,  shaking  it  .frequently.  When  solution  has  been  ef- 
fected, or  but  a  slight  residue  remains  undissolved,  filter  the 
liquid  and  add  enough  distilled  water  to  make  the  specific  weight 
of  the  product  from  1.087  to  1.091. 

This  solution  represents  from  4.8  to  5  per -cent  of  Fe.  It 
is,  therefore,  about  two-thirds  the  strength  of  the  solution  of  ferric 
acetate  of  the  U.S.P. 


IRON  ACETATE.  371 

Iron  Acetate  Tincture. 

TINCTURA    FERRI    ACETATIS   (U.S.P.,   l88o). 

Solution  of  ferric  acetate 86  ml 

Acetic  ether   45  ml 

Alcohol    74  ml 

Mix  the  alcohol  and  acetic  ether ;  then  add  the  solution  of  ferric 
acetate  slowly  and  in  small  quantities  at  a  time. 

Notes.  If  the  ferric  acetate  is  added  all  at  once,  heat  is  gen- 
erated, whereby  acetic  acid  and  acetic  ether  are  volatilized,  and 
the  preparation  is  liable  to  become  unclear  from  basic  ferric  ace- 
tate. 

Must  be  kept  in  a  well  stoppered  bottle  in  a  cool,  dark  place. 

The  "Tinctura  Ferri  Acetici  Aetherea"  of  the  German  Phar- 
macopoeia is  a  mixture  of  8  parts  of  the  solution  of  acetate  of  iron 
(G.P),  i  part  of  alcohol  (86%),  and  i  part  of  acetic  ether.  It  is 
nearly  identical  with  the  American  tincture  (1880)  as  to  the  per- 
centage of  iron  [the  American  tincture  'corresponding  to  about 
3.75%  and  the  German  to  about  3.90%  of  metallic  iron]. 

The  tincture  of  ferric  acetate  was  dropped  from  the  American 
Pharmacopoeia  in  the  revision  of  1890;  but  the  solution  of  ferric 
acetate  was  retained. 

Basham's  Mixture. 
[SOLUTION  OF  IRON  AND  AMMONIUM  ACETATE.] 


Tincture  of  ferric  chloride 20  ml 

Diluted  acetic  acid    . 30  ml 

Solution  of  ammonium  acetate 200  ml 

Aromatic  elixir   100  ml 

Glycerin    120  ml 

Water,  sufficient. 

Pour  the  solution  of  ammonium  acetate  into  a  suitable  container 
and  add  to  it,  successively,  the  diluted  acetic  acid,  tincture  of 
ferric  chloride,  elixir,  and  glycerin,  and,  finally,  enough  water  to 
make  the  total  product  measure  i  liter. 

This  preparation  should  be  prepared  only  as  wanted. 


372  IRON  ALBUMINATE. 

Notes.  The  solution  of  ammonium  acetate  used  should  not  be 
alkaline.  The  quantity  prescribed  of  diluted  acetic  acid  is  suffi- 
cient to  prevent  any  turbidity.  As  the  tincture  of  ferric  chloride 
is  added  the  color  changes  to  a  decidedly  red  because  of  the  forma- 
tion of  ferric  acetate.  The  preparation  should  be  perfectly  clear, 

IRON   ALBUMINATE. 
[Ferrated  Albumin.] 

Solution  of  ferric  oxychloride  (containing 

3.5%  of  Fe) 300  parts 

Dried  egg  albumen 75  parts 

Solution  of  sodium  hydroxide  (containing 
about  0.1%  of  NaOH). 

Distilled  water,  of  each  sufficient. 

Dilute  the  solution  of  ferric  oxychloride  with  10,000  parts  of 
water  of  the  temperature  of  50°  C. 

Dissolve  the  egg  albumen  in  10,000  parts  of  distilled  water  of 
the  same  temperature  as  before. 

Pour  the  solution  of  egg  albumen  slowly  and  with  constant 
stirring  into  the  solution  of  iron. 

Neutralize  the  mixture  carefully  and  exactly  with  solution  of 
sodium  hydroxide. 

The  iron  albuminate,  which  will  now  be  completely  precipitated, 
is  to  be  washed  with  distilled  water  until  the  washings  give  no 
further  reaction  for  chloride  (with  AgNO3).  Collect  the  precip- 
itate on  a  cloth  strainer,  let  it  drain  well,  squeeze  out  as  much  of 
the  water  contained  in  it  as  can  be  pressed  out  of  it  by  gentle 
pressure.  Spread  it  on  glass  plates,  and  dry  at  from  40°  to  50°  C. 

Description. — Red-brown  scales  or  powder,  odorless,  of  feebly 
ferruginous  taste,  forming  a  clear  solution  with  water  containing 
about  0.15%  of  sodium  hydroxide  in  solution.  It  contains  about 
20%  of  Fe. 

Solution  of  Albmninated  Iron. 

[After  the  Danish  Pharmacopoeia.] 

Dried  egg  albumen 10  parts 

Ferric  chloride 60  parts 

Cinnamon  water   100  parts 

Alcohol    50  parts 

Distilled  water,  sufficient. 


IRON  ALBUMINATE.  373 

Dissolve  the  egg  albumen  in  350  parts  of  distilled  water  at  a 
temperature  of  about  40°  C.  Strain  the  solution. 

Dissolve  the  ferric  chloride  in  430  parts  of  distilled  water. 

Pour  the  solution  of  egg  albumen  slowly,  and  during  uninter- 
rupted stirring,  into  the  solution  of  ferric  chloride. 

Heat  the  mixture  over  a  water-bath  at  a  temperature  of  90°  C. 
for  half  an  hour. 

Then  let  it  cool  and  add  to  it  the  cinnamon  water  and  alcohol, 
previously  mixed.  Finally  add  enough  distilled  water  to  make 
the  total  weight  of  the  final  product  1000  parts. 

Description. — A  fed-brown  liquid,  which  appears  clear  by  trans- 
mitted light,  but  unclear  by  reflected  light.  It  has  scarcely  any 
chalybeate  taste. 

Reduced  to  one-half  its  volume  by  evaporation  it  exhibits  an 
acid  reaction. 

When  heated  to  the  boiling  point  it  is  not  rendered  turbid,  nor 
does  the  addition  of  alcohol  make  it  unclear  (absence  of  albumin). 

If  a  few  drops  of  ammonia  water  or  diluted  hydrochloric  acid 
be  added  to  5  Gm  of  the  solution  of  ferrated  albumin  a  red-brown 
precipitate  is  formed.  But  5  Gm  of  the  solution  shaken  with  15 
Gm  of  ammonia  water  produces  a  clear  mixture. 

Potassium  carbonate  causes  it  to  gelatinize. 

The  preparation  contains  about  0.4  per  cent  of  Fe. 

Alkaline  Solution  of  Iron  Albuminate. 
[After  the  Swiss  Pharmacopoeia.] 

Fresh  egg  albumen 200  parts 

Solution  of  oxychloride  of  iron (3.5 %Fe)  120  parts 
Solution  of  sodium  hydroxide  ($% 

NaOH) 15  parts 

Alcohol    150  parts 

Cinnamon  water   100  parts 

Distilled  water,  sufficient. 

Mix  the  egg  albumen  with  4000  parts  of  distilled  water  heated 
to  a  temperature  of  50°  C. 

Mix  the  solution  of  ferric  oxychloride  with  4000  parts  of  dis- 
tilled water  heated  to  a  temperature  of  50°  C. 

Pour  the  solution  of  egg  albumen  slowly  and  with  uninter- 
rupted stirring  into  the  diluted  solution  of  oxychloride  of  iron. 


374  IRON   ARSENATE. 

Add  carefully  enough  solution  of  sodium  hydroxide  (of  0. 
strength)  to  render  the  liquid  perfectly  neutral. 

Wash  the  precipitated  ferrated  albumin  with  distilled  water  hav- 
ing the  temperature  of  50°  C.  until  the  washings  no  longer  give 
any  reaction  for  chloride. 

Collect  the  precipitate  on  a  strainer  and  let  it  drain  until  its 
weight  is  reduced  to  400  parts. 

Transfer  the  ferrated  albumin  to  a  bottle,  add  the  solution  of 
sodium  hydroxide  to  it,  and  mix  well. 

Then  add  the  alcohol  and  cinnamon  water  previously  mixed, 
and  finally  enough  distilled  water  to  make  the  total  weight  of  the 
product  looo  parts. 

Let  it  stand  until  any  solid  particles  shall  have  subsided,  and 
then  decant  the  clear  liquid,  or  filter  the  product  if  necessary. 


IRON  ARSENATE. 

FERRI  ARSENAS. 

Ferrous  sulphate  46  parts 

Sodium  arsenate,  dried  at  149°  C 35  parts 

Sodium  bicarbonate   10  parts 

Dissolve  the  sodium  arsenate  in  200  parts  of  boiling  distilled 
water,  and  the  ferrous  sulphate  in  240  parts  of  boiling  water ;  add 
the  solution  of  the  iron  salt  to  that  of  the  arsenate ;  then  add  the 
sodium  bicarbonate  previously  dissolved  in  120  parts  of  hot 
water.  Stir  well.  Collect  the  precipitate  on  a  wetted  muslin 
strainer  and  wash  it  with  water  until  the  washings  cease  to  be 
affected  by  test  solution  of  barium  chloride.  Press  out  the  water 
from  the  washed  precipitate,  folded  in  strong  linen,  in  a  screw 
press,  and  dry  the  product  on  porous  bricks  in  a  warm  air  cham- 
ber at  a  temperature  not  exceeding  40°  C. 

Notes,  The  reaction  is  analogous  to  that  occurring  in  the 
process  of  preparing  the  precipitated  ferroso-ferric  phosphate. 
The  precipitate  is  ferroso-ferric  arsenate,  of  variable  composition 
and  color. 

Description. — A  green  to  greenish-blue,  odorless  and  tasteless 
powder,  insoluble  in  water  and  alcohol. 


IRON  BENZOATE.  375 

IRON  BENZOATE. 

FERRI    BENZOAS. 

To  a  solution  of  ferric  chloride  add  ammonia  water  gradually 
as  long  as  no  precipitate  is  formed.  Then  add  a  solution  of  am- 
monium benzoate  until  precipitation  is  completed.  Collect  the 
precipitate,  wash  it  with  a  limited  amount  of  cold  water,  let  it 
drain  somewhat,  press  out  the  remaining  water  as  far  as  practi- 
cable, and  then  dry  the  product  without  the  aid  of  heat. 

Another  Method. 

Sodium   benzoate    5  parts 

Ferric  chloride 3  parts 

Distilled  water,  sufficient. 

Dissolve  the  sodium  benzoate  in  25  parts  of  distilled  water,  and 
the  ferric  chloride  in  40  parts  of  distilled  water. 

Pour  the  solution  of  ferric  chloride  slowly  into  the  solution  of 
sodium  benzoate,  stirring  constantly. 

Wash  the  precipitate  well  with  distilled  water,  let  it  drain,  and 
dry  it. 

Description. — The  product  is  a  (brownish)  flesh-colored,  odor- 
less and  tasteless  powder.  Sparingly  soluble  in  fixed  oils. 

IRON    BROMIDE. 

FERRI     BROMIDUM. 

FeBr2=2i6. 

Ferrous  bromide  in  water  solution  is  obtained  when  iron  and 
bromine  react  upon  each  other  in  water,  the  iron  being  used  in 
excess.  The  solution  is  bright  green.  Ferrous  bromide  in  the 
solid  state  can  not  -be  kept,  nor  does  a  water-solution  keep  with- 
out sugar. 

Syrup  of  Bromide  of  Iron. 

A  syrup  of  ferrous  bromide  is  sometimes  used,  which  contains 
10  per  cent  of  the  bromide,  keeps  well,  and  may  be  prepared  as 
follows : 


3/6  IRON  BROMIDE. 

Iron,  in  the  form  of  wire,  cut  into  small  pieces.     30  Gm 

Bromine  . 75  Gm 

Sugar,  in  coarse  powder 600  Gm 

Distilled  water,  sufficient. 

Introduce  the  iron  into  a  flask,  add  200  ml  of  distilled  water, 
and  afterward  the  bromine.  Shake  the  mixture  occasionally,  until 
the  reaction  ceases  and  the  solution  has  acquired  a  green  color  and 
has  lost  the  odor  of  bromine.  Place  the  sugar  in  a  porcelain  dish 
and  filter  the  solution  of  bromide  of  iron  into  the  sugar.  Rinse 
the  flask  and  iron  wire  with  90  ml  of  distilled  water,  and  p'ass  the 
washings  through  the  filter  into  the  sugar.  Stir  the  mixture  with 
a  glass  rod,  heat  it  to  the  boiling  point  on  a  sand-bath,  and,  having 
filtered  the  syrup  through  paper  into  a  tared  bottle,  add  enough 
distilled  water  to  make  the  product  weigh  1000  Gm.  Lastly, 
shake  the  bottle,  which  should  be  completely  filled,  securely  stop- 
pered, and  kept  in  a  place  accessible  to  daylight. 

Notes.  The  bromine  must  be  added  cautiously,  as  the  reaction 
is  sometimes  violent.  When  too  violent,  the  chemical  action  can 
be  controlled  by  keeping  the  flask  in  cold  water. 


IRON  SACCHARATED  CARBONATE. 

FERRI   CARBONAS   SACCHARATUS. 

Ferrous  sulphate   50  parts 

Sodium   bicarbonate    35  parts 

Sugar,  in  fine  powder,  sufficient. 

Dissolve  the  ferrous  sulphate  in  200  parts  of  boiling  distilled 
water,  and  the  sodium  bicarbonate  in  500  parts  of  distilled  water 
of  the  temperature  of  about  40°  to  50°  C.  Filter  the  solutions 
separately.  Put  the  bicarbonate  solution  into  a  flask  capable  of 
holding  1000  parts  of  water;  then  add  the  hot  solution  of  ferrous 
sulphate,  agitating  the  mixture  well,  and  when  the  effervescence 
has  subsided  fill  the  flask  at  once  with  boiling  distilled  water, 
cork  it  to  exclude  air,  and  set  it  aside  for  two  hours.  Then  re- 
move the  mother  liquor  by  means  of  a  siphon,  and  again  fill  the 
flask  with  boiling  distilled  water,  shake  it  well,  let  it  settle  once 
more,  and  repeat  the  washing  in  the  same  manner  until  the  wash 
water  produces  but  little  turbidity  with  test  solution  of  barium 


IRON    CARBONATE.  377 

chloride.  Then  transfer  the  precipitate  to  a  wetted  muslin 
strainer,  let  it  drain,  or  press  out  the  water,  and  mix  the  magma 
intimately  with  80  parts  of  sugar  in  a  porcelain  dish,  evaporate 
the  mixture  to  dryness  by  means  of  a  water-bath,  powder  the 
product,  adding  more  dry  powdered  sugar  if  necessary  to  make 
the  total  weight  of  the  product  100  parts,  and  keep  it  in  a  tightly 
corked  bottle. 

Reaction.     FeSO4+2NaHCO3=FeCO3.H2O+Na2SO,+CO2. 

Notes.  All  the  precautions  directed  by  this  formula  are  in- 
tended to  prevent  the  oxidation  of  the  precipitate  by  contact  with 
the  air.  Sodium  bicarbonate  is  substituted  for  the  normal  carbonate 
in  order  that  the  escaping  carbonic  acid  may  help  to  exclude  the 
air.  If  about  5  parts  of  sugar  be  added  to  the  solution  of  bicar- 
bonate of  sodium  before  the  iron  salt  is  poured  into  it,  and  if  the 
wash  water  also  be  sweetened  with  about  four  per  cent  of  sugar, 
the  oxidation  is  still  more  effectually  prevented.  Boiling  water  is 
used  in  order  that  no  air  may  be  contained  in  it ;  and  the  whole 
process  must  be  expeditiously  carried  to  its  completion  in  order 
not  to  expose  the  product  to  oxidation  longer  than  necessary. 
When  the  precipitate  has  been  mixed  with  the  sugar,  the  mixture 
should  not  be  stirred  any  more  than  is  necessary  during  the 
process  of  its  evaporation  to  dryness,  and  as  soon  as  the  mass  is 
sufficiently  dry  it  should  be  at  once  powdered  and  put  into  small 
bottles,  which  are  to  be  immediately  and  tightly  closed. 

Hager  recommends  the  use  of  milk  sugar  instead  of  cane  sugar 
to  facilitate  the  drying.  The  German  Pharmacopoeia  prescribes 
one-fourth  of  milk  sugar  and  three-fourths  of  cane  sugar  instead 
of  cane  sugar  alone. 

A  more  dense  precipitate  is  obtained  by  having  the  solutions  hot 
when  mixed.  But  the  solution  of  sodium  bicarbonate  can  not  be 
made  with  water  of  a  higher  temperature  than  50°  C,  beca'use 
the  bicarbonate  decomposes  if  subjected  to  a  much  higher  temper- 
ature than  that. 

Sugar  and  honey  aid  in  preventing  oxidation,  by  excluding  the 
air  from  the  product. 

See  also  the  notes  under  the  title,  Mass  of  Carbonate  of  Iron. 

Description. — A  grayish  or  greenish-brown  powder,  which  ox- 
idizes on  exposure  to  the  air. 


378  IRON    CARBONATE. 

Mass  of  Carbonate  of  Iron. 

[PILL   OF    CARBONATE   OF    IRON.       VALLEYS    MASS.] 

Ferrous  sulphate  100  parts 

Sodium  carbonate   no  parts 

Clarified   honey    38  parts 

Sugar,  in  coarse  powder 25  parts 

Syrup,  distilled  water,  each  sufficient. 

Dissolve  the  sulphate  of  iron  and  the  carbonate  of  sodium  sep- 
arately, each  in  two  hundred  parts  of  boiling  distilled  water,  and, 
having  added  twenty-five  parts  of  syrup  to  the  solution  of  the  iron 
salt,  filter  both  solutions.  Mix  when  cold,  in  a  bottle  just  large 
enough  to  hold  the  mixture,  or  add  enough,  distilled  water  to  fill 
it  ;•  cork  the  bottle  well,  and  set  it  aside,  that  the  carbonate  of  iron 
may  settle.  Pour  off  the  supernatant  liquid,  and,  having  mixed 
syrup  and  distilled  water  in  the  proportion  of  one  part  of  syrup 
to  sixteen  parts  of  water,  wash  the  precipitate  with  the  mixture 
until  the  washings  no  longer  have  a  saline  taste.  Drain  the  precip- 
itate on  a  flannel  cloth,  and  express  as  much  of  the  water  as 
possible.  Lastly,  mix  the  precipitate  immediately  with  the  honey 
and  sugar,  and,  by  means  of  a  water-bath,  evaporate  the  mixture, 
constantly  stirring,  until  reduced  to  one  hundred  parts. 

Notes.  The  reaction  is  given  under  the  title,  Subcarbonate  of 
Iron.  Compare  this  process  with  that  for  saccharated  carbonate 
of  iron.  The  ferrous  sulphate  must  be  in  crystals  in  no  degree  ef- 
floresced. Sodium  bicarbonate  may  be  used  here  as  well  as  in 
the  preceding  preparation  instead  of  the  normal  carbonate ;  75 
parts  of  bicarbonate  should  be  substituted  for  the  no  parts  of 
carbonate.  If  bicarbonate  is  used  the  solution  of  it  must  be  made 
not  with  boiling  water  but  with  water  of  a  temperature  not  ex- 
ceeding 50°  C.  The  use  of  hot  solutions  renders  the  precipitate 
more  dense,  which  is  of  material  advantage  in  the  preparation  of 
saccharated  ferrous  carbonate  and  Vallet's  mass,  where  expedi- 
tious washing  is  necessary. 

Description. — A  soft,  dark  grayish-brown  mass,  having  a  sweet, 
afterwards  ferruginous,  taste. 


IRON    CHLORIDE.  379 

IRON  (FERRIC)  CHLORIDE. 

FERRI    CHLORIDUM     (RUBRUAl). 

FeCl3+6H2O=:27o.2. 

Iron,  in  the  form  of  fine,  bright  wire,  and 

cut  into  small  pieces 15  parts 

Hydrochloric  acid, 

Nitric  acid, 

Distilled  water,  each,  a  sufficient  quantity. 

Put  the  iron  into  a  flask  capable  of  holding  two  or  three  hun- 
dred parts  of  water.  Add  54  parts  of  hydrochloric  acid  diluted 
with  25  parts  of  distilled  water. 

Let  the  mixture  stand  in  a  warm  place  until  effervescence  has 
nearly  ceased.  Then  heat  it  to  the  boiling  point  and  continue  the 
boiling  for  two  or  three  minutes. 

Let  the  liquid  cool  somewhat  and  then  filter  it,  while  still  hot, 
through  paper ;  and,  having  rinsed  the  flask  and  undissolved  iron 
with  a  little  hot  distilled  water,  pass  the  rinsings  also  through  the 
filter. 

Add  28  parts  of  hydrochloric  acid  to  the  filtrate ;  add  this  mix- 
ture, a  little  at  a  time,  to  8  parts  of  nitric  acid  contained  in  a 
capacious  porcelain  dish,  gently  warmed,  waiting  after  each  addi- 
tion until  the  copious  evolution  of  red  nitrous  vapors  subsides 
before  adding  more.  When  all  of  the  iron  solution  has  been 
added  to  the  nitric  acid,  and  active  effervescence  has  ceased,  heat 
the  dish  and  contents  by  means  of  a  sand-bath  until  the  liquid  is 
free  from  nitrous  odor. 

Then  test  a  few  drops  of  the  liquid,  diluted  with  water,  with 
freshly  prepared  potassium-ferricyanide  test-solution.  Should 
this  reagent  produce  a  blue  precipitate  or  a  blue  color,  add  a  little 
more  nitric  acid,  drop  by  drop,  to  the  hot  solution  of  ferric  chloride 
in  the  porcelain  dish,  as  long  as  any  further  evolution  of  red 
vapors  is  observed.  The  solution  is  then  tested  as  before,  and 
when  the  test-solution  of  potassium  ferricyanide  no  longer  pro- 
duces a  decidedly  blue  color,  showing  that  only  a  trace  of  ferrous 
chloride  remains  in  the  liquid,  no  more  nitric  acid  must  be  added. 

[Should  an  excess  of  nitric  acid  be  found  to  have  been  added, 
the  excess  must  be  expelled  by  heating  the  liquid  until  all  odor 
of  nitric  acid  has  ceased.] 


380  IRON    CHLORIDE. 

Then  add  5  parts  of  hydrochloric  acid  and  enough  distilled 
water  to  make  the  whole  weigh  60  parts. 

Set  the  dish  aside,  covered  with  glass,  in  a  cool  place,  until  a 
solid  crystalline  mass  is  formed  of  the  contents. 

Remove  the  crystalline  mass,  break  it  into  pieces,  and  keep  the 
product  in  glass-stoppered  bottles,  protected  from  light. 

Reactions.  First,  2Fe+4HCl=2FeCl2+2H2 ;  then,  6FeCl2+ 
6HCl+2HNO3=3Fe2Cl6+4H2O-f2NO. 

Notes.  The  iron  is  readily  dissolved  by  the  hydrochloric  acid, 
especially  in  the  beginning ;  as  the  solution  becomes  charged  with 
ferrous  chloride,  however,  the  action  is  slower  and  it  is  advan- 
tageous to  promote  it  by  the  aid  of  heat.  In  order  that  the  density 
of  the  solution  of  ferrous  chloride  may  not  be  so  great  as  to  retard 
the  chemical  action,  the  Pharmacopoeia  directs  that  the  hydro- 
chloric acid  be  diluted  before  the  iron  is  added.  The  evolution  of 
hydrogen  may  cease  before  all  the  HC1  is  decomposed  by  the  iron 
at  the  ordinary  temperature,  but  when  the  liquid  is  brought  to 
the  boiling  point  the  acid  is  completely  saturated. 

As  the  amount  of  hydrochloric  acid  saturated  with  iron  to  form 
ferrous  chloride  determines  the  strength  of  the  finished  solution 
and  the  amounts  of  hydrochloric  and  nitric  acids  required  to 
raise  that  ferrous  chloride  to  ferric  chloride,  it  is  important  that 
the  whole  quantity  of  hydrochloric  acid  first  used  be  completely 
saturated. 

Some  ferric  chloride  is  formed  before  the  acid  is  saturated, 
especially  if  the  iron  was  rusty ;  but  after  boiling  the  liquid  with 
the  excess  of  iron  present  the  solution  contains  ferrous  salt  only. 

The  solution  of  ferrous  chloride  is  then  to  be  treated  with 
hydrochloric  and  nitric  acids  to  convert  it  into  ferric  salt.  When 
the  solution  is  concentrated  this  may  be  accomplished  at  little 
above  ordinary  room  temperature.  When  the  solution  is  dilute, 
on  the  other  hand,  a  temperature  near  the  boiling  point  is  required 
to  complete  the  reaction.  A  good  rule  is  to  evaporate  the  solution 
of  ferrous  chloride  until  it  has  about  1.30  sp.  w.,  and  after  adding 
the  additional  quantity  of  hydrochloric  acid  prescribed,  to  add 
this  solution  slowly,  a  little  at  a  time,  to  the  nitric  acid.  If  all  of 
the  solution  of  ferrous  chloride  is  added  at  once,  the  reaction  is 
too  violent,  the  red  fumes  being  evolved  so  copiously  and  suddenly 


IRON    CHLORIDE.  381 

that  the  liquid  may  boil  over.     The  most  suitable  temperature  at 
which  the  reaction  may  be  carried  out  is  between  80°  and  90°  C. 

A  small  excess  of  nitric  acid  is  unavoidable  if  the  solution  is  to 
be  entirely  free  from  ferrous  salt.  A  greenish-brown  coloration 
with  test-solution  of  potassium  ferricyanide  is  allowable,  indicat- 
ing merely  traces  of  ferrous  salt.  But  the  excess  of  nitric  acid 
even  then  liable  to  be  present  requires  considerable  evaporation 
to  get  rid  of  it.  Long  continued  strong  heating  of  the  solution 
of  ferric  chloride  (to  drive  off  HNO3)  is  liable  to  result  in  de- 
composition with  the  formation  of  basic  ferric  chloride.  When 
the  solution  of  ferric  chloride  is  perfectly  free  from  nitrous  odor, 
and  contains  not  more  than  traces  of  ferrous  salt,  the  last  addi- 
tion of  hydrochloric  acid  is  made,  and  the  distilled  water  added. 
This  hydrochloric  acid  is  added  to  prevent  the  formation  of  basic 
chloride. 

The  Pharmacopoeia  directs  that  the  solution  shall  be  evaporated 
down  to  given  quantity  by  weight.  That  quantity  is  the  amount 
of  crystallized  ferric  chloride  produced  by  the  ferrous  chloride 
formed  by  the  saturation  of  the  hydrochloric  acid  first  used  (54 
parts)  with  the  iron. 

It  may  preferably  be  evaporated  down  until  a  small  sample 
taken  out  and  cooled  no  longer  gives  off  acid  vapors  in  the  air, 
nor  has  a  pronounced  odor  of  HC1,  and  the  liquid  has  about  1.62 
to  1.65  sp.  w.  at  25°  C.  This  procedure  is  always  necessary  in  cases 
where  any  portion  of  the  liquid  has  been  lost  by  accident  at  any 
stage  of  the  process. 

The  chloride  crystallizes  readily,  even  within  twelve  hours,  if 
of  proper  strength ;  but  may  not  solidify  for  several  weeks  if  too 
strong.  When  the  evaporation  has  been  carried  too  far,  the  liquid 
does  not  contain  enough  water  of  crystallization,  and  in  that  case 
it  must  be  placed  in  a  cool,  moist  atmosphere,  from  which  the 
necessary  additional  moisture  may  be  absorbed.  A  solution  con-' 
taining  just  enough  hydrochloric  acid  crystallizes  more  readily 
than  one  that  is  not  acid  enough,  and  yields  a  lighter-colored  and 
harder  crystalline  mass.  The  crystallization  also  proceeds  more 
satisfactorily  in  a  loosely  covered  dish  than  in  a  closely  covered 
vessel. 

Should  the  crystalline  mass  of  ferric  chloride  stick  to  the  dish 
so  tenaciously  that  its  removal  may  involve  the  danger  of  breaking 


382  IRON    CHLORIDE. 

the  vessel,  this  difficulty  may  be  avoided  bv  gentle  warming, 
whereby  the  cake  is  loosened. 

The  product  ought  to  be  dried  over  sulphuric  acid  or  over 
quick-lime. 

The  ferric  chloride  is  used  chiefly  for  preparing  aqueous  and 
alcoholic  solutions. 

Description. — Orange  yellow,  crystalline  masses  or  pieces,  hav- 
ing a  faint  odor  of  hydrochloric  acid  (sometimes  odorless  when 
quite  dry),  .and  a  strongly  styptic  taste.  Deliquescent  in  moist 
air.  Freely  soluble  in  water  and  in  alcohol. 

Ferrated  Ammonium  Chloride. 

[FLORES    MARTIS.] 

Ferric  chloride 2  parts 

Ammonium    chloride 18  parts 

Diluted  hydrochloric  acid i  part 

Distilled   water 60  parts 

Dissolve,  filter,  and  evaporate  the  filtrate  over  a  water-bath, 
during  constant  stirring,  to  dryness. 

Put  the  dry  product  at  once  in  a  glass  stoppered  bottle  and 
keep  it  protected  from  light. 

An  orange  yellow,  deliquescent  powder,  which  is  not  a  chemi- 
cal compound  but  a  mechanical  mixture  of  the  two  chlorides. 

It  contains  about  2  per  cent  of  Fe. 

Notes.  The  Swiss  Pharmacopoeia  orders  77  parts  of  solution  of 
ferric  chloride  (U.  S.  P.)  to  600  parts  of  ammonium  chloride, 
with  330  parts  of  water,  and  without  any  hydrochloric  acid ;  this 
solution  to  be  evaporated  to  dryness. 

The  German  Pharmacopoeia  orders  about  7  parts  of  solution  of 
ferric  chloride  (U.  S.  P.)  and  32  parts  of  H4NC1. 

Iron  (Ferric)  Chloride  Solution. 

LIQUOR     FERRI     CHLORIDI ;   U.    S. 

An  aqueous  solution  of  ferric  chloride,  containing  37.8  per 
cent  of  the  anhydrous  salt  [FeCl3=i62.2]  corresponding  to  62.9 
per  cent  of  the  crystallized  chloride  [FeClg-f- 6H2O=27O.2],  or 
to  about  13  per  cent  of  metallic  iron,  and  containing  also  some 


IRON    CHLORIDE.  383 

free  hydrochloric  acid  [about  1.6  per  cent  of  HC1,  equivalent  to 
5  per  cent  of  the  official  hydrochloric  acid]. 

The  official  solution  of  ferric  chloride  is  prepared  from  iron, 
hydrochloric  acid,  nitric  acid,  and  water  as  described  under  the 
title  of  Iron  Chloride.  The  quantities  of  the  materials  required 
to  make  one  hundred  parts  of  the  finished  solution  are : 

Iron,  in  the  form  of  fine  bright  wire,  cut 

into  small  pieces 15  parts 

Hydrochloric    acid .   87  parts 

Nitric  acid. 

Distilled  water,  each,  sufficient. 

The  iron  is  put  into  a  flask  capable  of  holding  at  least  twice  the 
volume  of  the  finished  product  to  be  made;  54  parts  of  hydro- 
chloric acid  and  25  parts  of  distilled  water  are  added;  the  com- 
plete saturation  of  the  acid  is  insured  by  the  aid  of  heat,  and  the 
ferrous  chloride  is  converted  into  ferric  chloride  by  means  of  28 
parts  of  hydrochloric  acid  and  8  parts  of  nitric  acid,  precisely  as 
described  under  the  title  of  ferric  chloride.  The  solution  is 
tested,  and  when  it  no  longer  contains  any  ferrous  salt  (or  when  it 
contains  only  traces  of  ferrous  chloride),  and  the  excess  of  nitric 
acid  has  been  dissipated  by  heat  so  that  no  nitrous  odor  is  re- 
tained by  the  liquid,  the  last  5  parts  of  hydrochloric  acid  is  added 
together  with  enough  distilled  water  to  make  the  whole  weigh 
100  parts  (instead  of  only  60  parts  as  prescribed  in  the  formula 
for  making  solid  crystalline  ferric  chloride). 

Notes.  The  reactions,  and  the  several  steps  of  the  process,  are 
explained  tinder  the  title,  Ferric  Chloride. 

A  solution  of  ferric  chloride  cannot  be  permanent  without  the 
presence  of  free  hydrochloric  acid.  In  the  absence  of  a  sufficient 
quantity  of  HC1,  a  basic  ferric  chloride  is  formed,  which  precipi- 
tates. To  redissolve  this  yellow  basic  salt  requires  more  hydro- 
chloric acid  than  it  takes  to  prevent  its  formation.  Continued 
heating  results  in  the  loss  of  HC1  and  the  formation  of  yellow 
oxychloride ;  if,  however,  sufficient  HC1  is  present,  no  precipitate 
is  formed,  but  the  solution  upon  being  heated  becomes  darker  in 
color,  a  ferric  chloride  with  5  molecules  of  water  being  formed. 
After  standing  some  time,  however,  the  darkened  solution  resumes 
its  original  color,  and  then  contains  the  chloride  with  12  mole- 
cules of  'water.  Weak  solutions  are  more  readily  altered,  and 


384  IRON    CHLORIDE. 

when  darkened  by  heating  do  not  resume  a  lighter  color  on  stand- 
ing. 

The  solution  of  ferric  chloride  often  contains  less  iron  than 
the  pharmacopoeial  standard  of  strength  requires.  This  may  be 
the  result  of  the  employment  of  hydrochloric  acid  not  of  the  full 
official  strength,  or  of  the  incomplete  saturation  of  the  acid  with 
iron. 

The  preparation  is  frequently  found  to  be  contaminated  with 
nitric  acid,  or  to  contain  some  ferrous  chloride;  it  can  not  con- 
tain both  ferrous  salt  and  free  nitric  acid  except  for  a  very  brief 
period  during  the  process  of  preparation,  and  then  only  traces  of 
each.  The  presence  of  a  trace  of  ferrous  chloride  can  not  be 
considered  as  a  very  serious  defect,  for  the  solution  is  used 
almost  exclusively  for  the  purpose  of  preparing  the  tincture  of 
chloride  of  iron  which  unavoidably  contains  a  large  amount  of 
ferrous  salt  formed  by  the  reducing  action  of  the  alcohol  upon 
the  ferric  chloride. 

But  the  presence  of  free  nitric  acid  is  more  objectionable. 
Hence  it  is  better  to  use  a  trifle  less  nitric  acid  than  is  necessary  to 
completely  remove  all  traces  of  ferrous  salt,  than  to  use  a  trifle  too 
much  so  as  to  leave  an  excess  of  that  acid,  because  the  expulsion 
of  the  excess  of  nitric  acid  by  heating  the  liquid  is  almost  impos- 
sible without  the  great  risk  of  causing  the  formation  of  basic 
ferric  chloride  by  oxidation,  a  corresponding  amount  of  hydro- 
chloric acid  (formed  from  the  decomposing  ferric  chloride)  being 
evolved  from  the  hot  liquid. 

Sunlight  slowly  decomposes  ferric  chloride  (solid  as  well  as  in 
solution)  into  ferrous  chloride  and  chlorine.  In  the  presence 
of  organic  substances,  such  as  alcohol  and  other  reducing  agents, 
this  reduction  is  much  more  rapid. 

Solution  of  ferric  chloride  may  also  be  prepared  by  dissolving 
ferric  hydroxide  in  hydrochloric  acid ;  but  a  strong  solution  can 
not  be  made  in  that  way  because  undiluted  hydrochloric  acid  is 
of  only  32  per  cent  strength  and  recently  precipitated  ferric  hy- 
droxide contains  much  water  which  would  further  dilute  the  solu- 
tion thus  formed.  If  the  official  hydrochloric  acid  be  used,  and  a 
ferric  hydroxide  free  from  water  were  employed  to  form  the  solu- 
tion of  ferric  chloride  according  to  the  equation : 

Fe(OH)a+3HCl=FeCl8+3H20 


IRON    CHLORIDE.  385 

the  resulting  solution  would  still  contain  only  about  36  per  cent 
of  FeCl3. 

As  1000  Gm  of  the  official  solution  of  ferric  sulphate  (contain- 
ing 27.8  per  cent  of  that  salt)  corresponds  to  225.2  Gm  of  ferric 
chloride  (FeCl3)  it  follows  that  if  the  ferric  hydroxide  precipi- 
tated from  1000  Gm  of  the  solution  named  is,  after  the  washing, 
subjected  to  strong  pressure  and  thus  reduced  to  not  over  640 
Gm  weight,  and  486  Gm  of  official  hydrochloric  acid  be  then 
added,  making  the  total  weight  of  the  product  1126  Gm,  the  solu- 
tion of  ferric  chloride  thus  obtained  will  contain  20  per  cent  of 
FeQ3,  together  with  a  very  slight  excess  of  HC1  (less  than  0.2%). 

When  the  solution  of  ferric  chloride  is  prepared  from  a  solu- 
tion of  ferrous  chloride,  the  conversion  of  the  ferrous  chloride 
into  ferric  chloride  may  be  effected  by  conducting  chlorine  gas 
into  the  solution  of  ferrous  chloride.  This  method  is  advantage- 
ous because  it  affords  a  product  absolutely  free  from  both  FeCl2 
and  HNO3. 

Some  pharmacopoeias  direct  that  the  solution  of  ferric  chloride 
be  made  by  dissolving  the  crystalline  ferric  chloride  in  distilled 
water,  which  is  a  direct,  convenient  and  definite  method. 

The  official  solution  of  ferric  chloride  (U.  S.  P.),  containing 
slightly  more  than  13  per  cent  of  Fe,  corresponding  to  37.8  per 
cent  of  FeCl3,  or  62.9  per  cent  of  FeCl3.6H2O,  or  to  18.63  Per 
cent  Fe2O3,  or  to  24.93  per  cent  of  ferric  hydroxide,  compares  in 
iron  strength  to  the  official  solution  of  ferric  sulphate  (U.  S.  P.) 
as  162  to  100;  in  other  words  100  parts  of  solution  of  ferric 
chloride  contains  as  much  iron  as  is  contained  in  162  parts  of 
solution  of  ferric  sulphate.  In  preparing  ferric  hydroxide  from 
solution  of  ferric  chloride,  100  parts  of  the  solution  will  require 
about  135  parts  of  official  ammonia  water  (10%)  to  insure  a  suf- 
ficient excess  of  ammonia. 

The  solution  of  ferric  chloride  of  the  German  and  Swiss  Phar- 
macopoeias contains  10  per  cent  of  Fe;  hence  about  77  parts 
of  that  solution  equals  100  parts  of  the  solution  of  the  U.  S.  P. 

The  Danish  and  Norwegian  Pharmacopoeias  contain  a  solution 
made  of  equal  parts  of  crystallized  ferric  chloride  and  distilled 
water. 

Thus  that  solution  is  nearly  identical  with  that  of  the  German 
and  Swiss  Pharmacopoeias. 

The  "liquor  ferri  perchloridi  fortis"  of  the  British  Phanna- 

Vol.   11—25 


386  IRON    CHLORIDE. 

copoeia  (1898)  has  the  sp.  w.  1.42  and  100  ml  of  it  contains  22.5 
grams  of  iron ;  in  other  words,  142  grams  of  the  solution  contains 
22.5  grams  of  iron,  which  corresponds  to  15.845  per  cent  of  metal- 
lic iron.  Thus  820  grams  of  the  British  "strong  solution  of  fer- 
ric chloride"  exactly  equals  1000  grams  of  the  American  "solu- 
tion of  ferric  chloride."  But  the  British  Pharmacopoeia  also  con- 
tains a  weaker  preparation  called  "solution  of  ferric  chloride" 
(the  English  title  being  identical  with  that  of  the  American  prep- 
aration), which  is  made  by  mixing  I  volume  of  the  strong 
solution  of  ferric  chloride  with  3  volumes  of  distilled  water  and, 
therefore,  contains  an  amount  of  ferric  chloride  corresponding 
to  5.09  per  cent  of  metallic  iron.  Thus  2552  grams  of  the  British 
solution  of  ferric  chloride  equals  1,000  grams  of  the  American 
solution  of  ferric  chloride. 

The  British  "strong  solution  of  ferric  chloride"  contains  about 
46  per  cent  of  anhydrous  ferric  chloride,  corresponding  to  7^-54 
per  cent  of  crystallized  ferric  chloride.  The  British  "solution 
of  ferric  chloride"  contains  about  14.83  per  cent  of  anhydrous 
ferric  chloride,  corresponding  to  about  24.68  per  cent  of  the  crys- 
tallized salt  (FeQ3.6H2O). 

The  solution  of  ferric  chloride  of  the  Pharmacopoeia  of  the 
Netherlands  is  prepared  by  dissolving  3  parts  of  ferric  chloride 
in  i  part  of  water.  It  is  described  as  containing  14.4  to  15.5  per 
cent  of  Fe,  and  having  the  sp.  w.  1.441  to  1.488. 

Description. — The  solution  of  ferric  chloride  of  the  American 
Pharmacopoeia  is  a  reddish-brown  liquid  having  but  a  faint  odor 
(and  that  the  odor  of  hydrochloric  acid  only).  It  has  a  strongly 
styptic  ferruginous  taste  and  an  acid  reaction.  Sp.  w.  1.387 
at  15°. 

Method  after  the  Swiss  Pharmacopoeia  (1893). 

Iron,    in    fine,   bright   wire,    cut    in    small 

pieces I  part 

Hydrochloric  acid  (32%  of  HQ) 4  parts 

Distilled  water,  sufficient. 

Put  the  iron  and  hydrochloric  acid  in  a  suitable  vessel  of  glass 
or  porcelain  in  a  warm  place.  When  effervescence  has  ceased 
heat  the  liquid  at  the  boiling  point  for  a  few  minutes.  Filter  the 
solution. 


IRON    CHLORIDE.  387 

Conduct  a  current  of  washed  chlorine  into  the  solution  until 
the  liquid  no  longer  produces  a  blue  precipitate  with  test-solution 
of  potassium-ferricyanide. 

Then  evaporate  the  solution  until  reduced  to  five  times  the 
weight  of  the  iron  dissolved,  cover  it  and  set  it  aside  in  a  cool 
place  to  crystallize.  Dry  the  crystalline  mass  over  sulphuric 
acid  (or  over  lime),  and  dissolve  the  ferric  chloride,  thus  dried, 
in  an  equal  weight  of  distilled  water. 

This  solution  contains  about  50  per  cent  of  crystallized  ferric 
chloride  corresponding  to  about  10  per  cent  of  metallic  iron. 

Notes.  To  ascertain  the  amount  of  iron  dissolved  in  the  hy- 
drochloric acid,  the  undissolved  portion  of  the  metal  must  be  col- 
lected and  weighed  and  its  weight  deducted  from  the  quantity 
originally  put  into  the  acid. 

The  solution  of  ferrous  chloride  may,  if  most  convenient,  be 
put  into  a  series  of  Woulff  bottles  connected  with  each  other  and 
with  the  wash-bottle  through  which  the  chlorine  gas  is  passed 
from  the  generator.  Only  the  solution  in  the  last  Woulff  bottle 
need  be  tested  with  the  solution  of  potassium-ferricyanide. 

It  is  well,  also,  to  connect  the  last  Woulff  bottle  with  another 
bottle  containing  sodium  carbonate  solution  in  order  to  fix  the 
excess  of  chlorine  passing  beyond  the  last  Woulff  bottle  so  as 
to  prevent  its  escape  into  the  room. 

The  Pharmacopoeia  of  the  Netherlands,  also,  directs  the  use 
of  chlorine  to  "oxidize"  the  ferrous  chloride  to-  ferric. 

It  will  be  seen  that  by  this  process  we  first  make  crystallized 
ferric  chloride,  and  then  make  the  solution  out  of  that  finished 
chloride.  It  would,  therefore,  be  as  well  to  divide  the  working 
formula  accordingly  into  two — giving  one  formula  for  the  prep- 
aration of  the  dried  crystallized  ferric  chloride,  and  a  separate 
one  for  the  preparation  of  the  solution. 

Iron  (Ferric)  Chloride  Tincture. 

TINCTURA    FERRI    CHLORIDI. 

The  official  tincture  of  chloride  of  iron  is  "a  hydroalcoholic  so- 
lution of  ferric  chloride  [FeCl3=  162.2],  containing  about  13.6 
per  cent  of  the  anhydrous  salt,"  corresponding  to  22.6  per  cent 


388  IRON    CHLORIDE. 

of  crystalline  ferric  chloride  (FeCl3+6H2O=27O.2),  or  to  about 
4.7  per  cent  of  metallic  iron. 

[It  should  be  understood,  however,  that  the  official  preparation 
contains  not  only  ferric  chloride,  alcohol  and  water,  but  also  a 
large  proportion  of  ferrous  compound  together  with  aldehyde 
and  chlorinated  ethereal  compounds  formed  by  reaction  between 
the  alcohol  and  the  ferric  chloride.] 

It  is  prepared  as  follows : 

Solution  of  ferric  chloride 250  volumes 

Alcohol,  sufficient  to  make  the  prod- 
uct 1000  volumes. 

Mix  the  liquids,  and  let  the  mixture  "stand,  in  a  closely  cov- 
ered vessel,  at  least  three  months ;  then  transfer  it  to  glass-stop- 
pered bottles,  and  keep  it  protected  from  light." 

Notes.  We  are  informed  that  the  object  of  letting  the  mixture 
of  alcohol  and  solution  of  ferric  chloride  stand  for  "at  least  three 
months"  is  the  formation  of  "certain  chlorinated  ether  com- 
pounds." 

Several  writers  attribute  the  formation  of  the  ethereal  com- 
pounds to  the  reaction  of  the  free  hydrochloric  acid  (contained  in 
the  solution  of  the  ferric  chloride)  upon  the  alcohol;  but  this  can 
not  be  true  because  a  liquid  containing  only  1.6  per  cent  of  HC1 
does  not  react  upon  alcohol  at  all. 

The  ethereal  products  are  formed  by  reaction  between  the  ferric 
chloride  and  the  alcohol,  and  the  principal  reactions  are  probably 
the  following: 

FeCl8+3C2HBOH=Fe(OH)8+3C2HBCl,  and 
2FeCl3+C2H5OH=2FeCl2+2HCl+C2H4O. 

The  ferric  hydroxide  formed  by  the  reaction  first  stated  is  not 
at  once  precipitated.  It  remains  dissolved  in  the  liquid  forming 
a  soluble  compound  with  the  undecomposed  portion  of  the  ferric 
chloride.  But  a  "basic  ferric  chloride"  or  "oxychloride"  of  iron 
is  finally  thrown  down. 

That  aldehyde  and  ethyl  chloride  are  both  contained  in  a  tinc- 
ture of  ferric  chloride  may  be  at  once  discovered  even  by  the 
sense  of  smell. 


IRON    CHLORIDE.  389 

The  hydrochloric  acid  formed  simultaneously  with  the  alde- 
hyde is  not  sufficient  to  form  FeCls  with  all  the  Fe(OH)3  formed 
with  the  ethyl  chloride. 

As  the  quantity  of  FeCl3  diminishes  and  the  amount  of  FeCl2 
increases,  the  preparation  becomes  materially  lighter  in  color. 

These  reactions  take  place  very  slowly  or  not  at  all  when  the 
mixture  is  kept  in  a  dark  place ;  they  progress  rapidly  when  it  is 
exposed  to  direct  sunlight. 

The  Pharmacopoeia  says  that  "after  the  tincture  has  been  ex- 
posed for  some  time  to  daylight  it  yields  a  greenish  or  greenish- 
blue  color  with  potassium-ferricyanide  test-solution,  showing  the 
presence  of  some  ferrous  salt  due  to  reduction."  But  while  the 
formation  of  the  ethyl  chloride  goes  on  most  rapidly  when  the 
tincture  is  freely  exposed  to  light,  it  can  not  proceed  far  without 
resulting  in  the  separation  of  iron  (as  basic  ferric  hydroxide  and 
oxychloride),  and  consequently  in  the  diminution  of  the  iron 
strength  of  the  preparation. 

The  Pharmacopoeia  fails  to  state,  but  probably  intends,  that 
the  mixture  of  alcohol  and  solution  of  ferric  chloride  should  be 
protected  against  light  during  the  prescribed  three  months  stand- 
ing as  well  as  afterwards.  If  thus  protected  the  preparation  will 
contain  very  little,  if  any,  of  either  ethyl  chloride  or  aldehyde. 
If,  on  the  other  hand,  the  presence  of  these  ethereal  substances  is 
desirable,  exposure  to  light  would  seem  to  be  necessary  to  obtain 
any  considerable  quantity  of  them. 

When  tincture  of  ferric  chloride  is  exposed  to  full  direct  sun- 
light for  a  sufficiently  long  time  it  finally  acquires  a  very  pale 
amber  color,  or  becomes  almost  colorless.  Preparations  so  made, 
sometimes  containing  added  ether  and  sometimes  not,  were  and 
are  to  be  found  in  the  pharmacopoeias  of  various  countries. 

The  addition  of  the  citrate  of  either  potassium,  sodium  or  am- 
monium, changes  the  color  of  the  tincture  of  ferric  chloride  to 
a  bright  green  and  also  removes  the  styptic  taste.  A  preparation 
called  "tincture  of  citro-chloride  of  iron"  [and,  sometimes,  very 
incorrectly,  "taste-less  tincture  of  chloride  of  iron"]  is  contained 
in  the  National  Formulary  of  the  American  Pharmaceutical  Asso- 
ciation. What  iron-compound  this  preparation  contains  is  not 
known. 

Description. — The  American  tincture  of  chloride  of  iron  is  a 
clear  brownish-red  liquid  having  a  peculiar  odor  suggestive  of 


39O  IRON    CHLORIDE. 

aldehyde  and  ethereal  compounds.     It  has  a  styptic  ferruginous 
taste  and  an  acid  reaction.     Sp.  w.  0.960  at  15°. 

Tinctura  Ferri  Chlorati  Aether e a 
of  the  German  Pharmacopoeia  is  prepared  as  follows : 

Solution  of  ferric  chloride  (G.  P.) I  part 

Ether I  part 

Alcohol  (86%) 7  parts 

Mix  the  liquids,  put  the  mixture  in  a  bottle  of  white  glass 
and  set  it  in  full  sunlight  until  wholly  decolorized.  Then  put  the 
bottle  in  a  shaded  place,  and  remove  the  stopper  occasionally  to 
admit  air,  until  the  liquid  acquires  a  yellow  color. 

Notes.  Light  causes  reaction  between  the  ferric  chloride  and 
alcohol,  resulting  in  the  formation  of  ferrous  chloride,  aldehyde 
and  hydrochloric  acid,  and  also  ethyl  chloride  and  water.  When 
the  liquid  is  now  put  in  a  shaded  place  and  the  stopper  of  the 
bottle  removed  from  time  to  time,  the  ferrous  chloride  is  oxidized 
by  the  air  and  some  basic  ferric  chloride  is  formed  which  colors 
the  solution  yellow.  A  part  of  the  aldehyde  is  at  the  same  time 
oxidized  to  acetic  acid,  perhaps  partly  by  the  aid  of  some  free 
chlorine  formed  while  the  liquid  was  exposed  to  light. 

The  finished  ethereal  tincture  of  chloride  of  iron,  therefore, 
contains  alcohol,  ferric  chloride,  ferrous  chloride,  ethyl  chloride, 
aldehyde,  acetic  acid,  and  basic  ferric  chloride. 

IRON  (FERROUS)  CHLORIDE. 

FERRI    CHLORIDUM     (VIRIDE). 

FeCl24H2O==i98.8. 

Iron   wire I  part 

Hydrochloric  acid 4  parts 

Distilled   water 2  parts 

Dissolve  the  iron  in  the  acid  and  water,  previously  mixed ; 
when  effervescence  has  ceased,  heat  to  boiling.  Let  settle,  de- 
cant, wash  the  undissolved  iron  with  a  little  water,  adding  the 
washings  to  the  decanted  liquor,  filter  while  hot,  and  crystallize. 


IRON   CITRATE.  39 1 

Remove  the  crystals   from  the  mother  liquor,  drain  them  in  a 
funnel,  and  put  them  at  once  in  a  bottle. 

Reaction.     Fe2+4HCl=2FeCl2+2H2. 

Description. — Large,  bluish-green,  transparent  crystals.  Odor- 
less. Taste  astringent,  ferruginous.  Readily  soluble  in  water  and 
in  glycerin. 

Oxidizes  on  exposure  to  air,  and  can  not  be  effectively  pro- 
tected against  oxidation  except  by  submerging  the  crystals  in 
some  liquid  in  which  the  chloride  is  insoluble. 


IRON  (FERRIC)   CITRATE. 

FERRI    CITRAS. 

Evaporate  any  convenient  quantity  of  the  solution  of  ferric 
citrate  over  a  water-bath  at  a  temperature  not  exceeding  60°  C. 
to  the  consistence  of  syrup,  and  spread  it  on  glass  plates  to  dry 
in  scales. 

Keep  it  in  well  stoppered  bottles  in  a  cool,  dark  place. 

Description. — Thin,  transparent,  garnet-red  scales,  odorless,  of 
slightly  ferruginous  and  only  slightly  acidulous  taste.  Freely 
soluble  in  water;  quickly  in  hot  water.  Insoluble  in  alcohol.  It 
gradually  loses  its  ready  solubility  in  water,  and  more  rapidly 
when  exposed  to  light.  The  percentage  of  iron  is  from  19  to 
20%,  but  it  varies;  and  the  percentage  of  moisture  retained  by 
the  scales  is  also  variable.  The  preparation  nearly  corresponds 
to  FeC6H5Or3H.,O,  but  may  contain  less  iron  and  more  water 
than  that  formula  indicates.  It  is,  therefore,  not  a  definite  chemi- 
cal compound. 

German  Official  Method. 

Solution  of  ferric  chloride,  U.  S.  P 20  parts 

Ammonia  water 27  parts 

Citric  acid 9  parts 

Distilled  water,  sufficient. 

Dilute  the  solution  of  ferric  chloride  with  100  parts  of  dis- 
tilled water,  and  the  ammonia  water  with  75  parts  of  distilled 
water.  Pour  the  iron  solution  slowly  and  during  uninterrupted 


392  IRON  CITRATE. 

stirring  into  the  dilute  ammonia  solution.  Wash  the  precipitate 
well  with  cold  distilled  water  in  the  usual  way. 

Dissolve  the  citric  acid  in  35  parts  of  distilled  water.  Add  the 
ferric  hydroxide  to  the  citric  acid  solution  in  a  porcelain  dish, 
and  heat  the  mixture  at  not  over  50°  C,  stirring  frequently,  until 
the  solution  is  saturated  or  the  ferric  hydroxide  nearly  all  dis- 
solved. 

Filter  the  solution,  evaporate  it  at  not  over  50°  C.  to  the  con- 
sistence of  syrup,  and  scale  the  product  in  the  usual  way  (see 
other  formulas  for  scale  salts). 

Ammonio-Ferric  Citrate. 

Solution  of  ferric  citrate 3  parts 

Ammonia  water I  part 

Mix  and  evaporate  the  mixture  over  a  water-bath  at  not  over 
60°  C.  to  the  consistence  of  thick  syrup ;  spread  this  on  glass 
plates  and  let  it  dry  in  scales. 

Keep  the  product  in  a  well  stoppered  bottle,  in  a  cool,  dark  place. 

Notes.  For  making  this  preparation  some  formulas  prescribe 
that  three  parts  of  citric  acid  dissolved  in  water  be  saturated 
with  ferric  hydroxide  as  described  in  the  notes  under  Solution  of 
Ferric  Citrate,  and  that  one  part  of  citric  acid,  saturated  with 
ammonia,  be  afterwards  added,  and  the  solution  evaporated  to 
form  scales. 

In  the  official  formula  of  America  the  proportions  prescribed 
of  the  materials  are:  100  volumes  of  solution  of  ferric  citrate 
and  40  volumes  of  ammonia  water,  which  proportions  correspond 
to  3  parts  and  i  part  by  weight. 

Description. — Thin,  transparent,  garnet-red  scales ;  odorless ; 
taste  slightly  saline  and  faintly  ferruginous.  Completely  and 
quickly  soluble  in  water.  Insoluble  in  alcohol. 

Another  Method. 
[After  the  Swiss  Pharmacopoeia.] 

Solution  of  ferric  chloride,  U.  S.  P 154  parts 

Citric  acid 70  parts 

Ammonia  water. 

Distilled  water,  of  each  sufficient. 


IRON  CITRATE.  393 

Dilute  the  solution  of  ferric  chloride  with  600  parts  of  distilled 
water. 

Dilute  200  parts  of  ammonia  water  with  600  parts  of  distilled 
water. 

Add  the  iron  solution  gradually  and  with  constant  stirring  to 
the  dilute  ammonia  solution.  Wash  and  drain  the  precipitate 
in  the  usual  way  and  forcibly  press  out  as  much  of  the  water  as 
practicable  from  the  magma. 

Dissolve  the  citric  acid  in  140  parts  of  distilled  water,  adding 
enough  ammonia  water  to  produce  a  slightly  alkaline  reaction. 
Filter. 

Dissolve  the  ferric  hydroxide  in  the  solution  of  ammonium 
citrate  with  the  aid  of  heat  applied  by  means  of  a  water-bath  and 
not  exceeding  50°  C. 

Evaporate  the  solution  to  a  syrupy  consistence,  spread  it  on 
glass  plates,  and  let  it  dry  to  form  scales. 

Iron  (Ferric)  Citrate  Solution. 

LIQUOR    FERRI    CITRATIS  ;    U.    S. 

Solution  of  normal  ferric  sulphate 105  parts 

Citric  acid 30  parts 

Ammonia  water  (10%  of  H3N) 90  parts 

Distilled  water. 

Mix  the  ammonia  water  with  300  parts  of  cold  water,  and  the 
iron  solution  with  1000  parts  of  cold  water.  Add  the  cold  di- 
luted iron  solution  gradually  to  the  ammonia  solution,  stirring 
constantly.  Let  the  precipitated  ferric  hydroxide  subside,  and 
decant  the  supernatant  liquid.  Pour  the  remaining  liquid,  con- 
taining the  magma,  upon  a  wetted  muslin  strainer ;  let  it  drain ; 
return  the  precipitate  to  the  precipitation  vessel  and  mix  it  well 
with  1500  parts  of  cold  water.  Let  settle,  decant,  and  again 
drain  the  magma  on  the  muslin  strainer.  Repeat  this  washing 
several  times,  until  the  washings  give  but  a  slight  cloudiness  when 
mixed  with  test-solution  of  barium  chloride.  Finally  let  the  fer- 
ric hydroxide  be  well  drained.  Then  place  it  in  a  strong  press 
cloth  and  forcibly  express  from  it,  by  means  of  a  screw  press,  as 
much  as  possible  of  the  water.  [The  magma  obtained  from  105 


394  IRON  CITRATE. 

parts  of  solution  of  ferric  sulphate  may  be  pressed  until  the  press 
cake  weighs  less  than  65  parts.] 

Put  the  citric  acid  in  a  porcelain  dish  and  add  to  it  about  one- 
half  its  weight  (15  parts)  of  distilled  water.  Place  the  dish 
over  a  water-bath  and  keep  its  contents  at  a  temperature  not 
exceeding  40°.  Add  the  press  cake  of  ferric  hydroxide,  in  small 
portions  at  a  time,  stirring  well,  and  allowing  each  portion  to 
dissolve  before  adding  another.  When  about  three  fourths  of 
the  ferric  hydroxide  has  been  added,  raise  the  temperature  of  the 
contents  of  the  dish  to  50°,  and  when  all  of  the  ferric  hydroxide 
has  been  added  let  the  temperature  be  increased  to  60°,  and  con- 
tinue heating  and  stirring  for  about  fifteen  minutes,  taking  care 
not  to  allow  the  temperature  to  rise  above  60°.  Filter  the  solu- 
tion and  evaporate  it  at  a  temperature  not  exceeding  60°  until  it 
weighs  100  parts. 

Keep  the  product  in  well  closed  bottles  in  a  cool  place  and  pro- 
tected from  light. 

Reactions. 

Fe.(S04)3+6H4NOH=2Fe(OH)3+3(H4N)2S04;  then 
Fe(OH)3+H3C6H507=FeC6H507+3H20. 

Notes.  The  pharmacopoeial  directions  do  not  require  that  the 
water  should  he  squeezed  out  of  the  magma  of  ferric  hydroxide, 
nor  that  the  hydroxide  shall  be  added  gradually  to  the  citric  acid 
mixed  with  a  little  water.  The  Pharmacopoeia  instead  directs  that 
the  drained  magma  be  at  once  mixed  with  the  citric  acid  and 
the  mixture  heated  at  60°  until  the  precipitate  (the  hydroxide) 
is  dissolved.  It  is  better,  however,  to  proceed  as  here  described, 
adding  gradually  the  ferric  hydroxide,  deprived  of  as  much  water 
as  can  be  pressed  out  of  it,  and  raising  the  temperature  to  60°  only 
at  the  end.  By  proceeding  in  this  manner  the  saturation  of  the 
citric  acid  will  be  effected  without  exposing  the  ferric  hydroxide 
or  the  solution  of  ferric  citrate  to  that  high  temperature  any  longer 
than  is  unavoidable,  and  the  concentration  of  the  solution  to  the 
required  standard  requires  but  little  evaporation. 

Ferric  hydroxide  is  easily  decomposed  and  rendered  insoluble, 
or  difficultly  soluble,  by  heat.  But  a  higher  heat  than  the  tempera- 
ture of  the  room  is  necessary  to  effect  the  solution  of  the  ferric 


IRON  CITRATE.  395 

hydroxide  in  the  citric  acid  solution,  and  especially  so  when  sat- 
uration is  approached. 

If  i  ml  of  ammonia  water  of  ten  per  cent  (H3N)  strength  be 
added  to  the  citric  acid  and  water  before  the  ferric  hydroxide  is 
added,  the  solution  of  the  latter  is  greatly  hastened  and  this  small 
quantity  of  ammonia  should  not  be  objected  to,  amounting  to  only 
i  Gm  of  H3N  in  each  liter  of  finished  product. 

A  small  amount  of  the  ferric  hydroxide  remains  undissolved, 
and  is  filtered  away  before  the  solution  is  evaporated  to  100  Gm. 
This  undissolved  hydroxide  is  usually  basic  owing  to  the  expos- 
ure of  the  normal  hydroxide  to  heat.  i 

Examinations  made  of  many  samples  of  solution  of  ferric  cit- 
rate and  of  the  ferric  citrate  in  scales  show  that  the  percentage 
of  iron  in  these  preparations  is  quite  variable.  This  is  due  to 
the  varying  degree  of  care  observed  in  their  manufacture,  and 
especially  to  the  conversion  of  a  greater  or  less  portion  of  the 
ferric  hydroxide  into  insoluble  meta-hydroxide.  It  is  intended 
that  the  citric  acid  shall  be  saturated  with  ferric  hydroxide,  but 
the  fact  that  a  portion  of  the  hydroxide  remains  undissolved  at 
the  end  does  not  indicate  saturation  if  the  undissolved  portion 
consists  of  basic  ferric  hydroxide  for  that  is  insoluble.  Hence  it 
is  necessary  in  order  to  obtain  as  nearly  uniform  results  as  prac- 
ticable, to  adopt  all  the  precautions  described  in  the  working  di- 
rections given  in  the  foregoing  formula. 

The  Pharmacopoeia  states  that  the  solution  is  of  a  strength 
corresponding  to  about  7.5  per  cent  of  metallic  iron.  This  is  a 
minimum  of  iron.  When  well  made  the  solution  must  contain 
about  35.5  per  cent  of  normal  ferric  citrate,  that  being  the  pro- 
portion of  ferric  citrate  formed  by  the  quantity  of  citric  acid  em- 
ployed. Assuming  that  the  citric  acid  is  all  neutralized  so  as  to 
form  normal  ferric  citrate,  the  finished  preparation  contains  about 
8  per  cent  of  iron.  One  hundred  grams  of  the  solution  should, 
upon  evaporation,  yield  about  42.5  per  cent  of  scaled  ferric  cit- 
rate; hut  the  yield  depends  in  part  upon  how  far  the  solution  is 
evaporated  before  it  is  put  on  the  glass  plates  to  be  dried,  and  the 
temperature  at  which  the  scaling  is  effected,  or,  in  other  words, 
the  amount  of  moisture  retained  by  the  scaled  salt.  If  the  scaled 
salt  correspond  to  FeC6H5O7.3H2O,  the  yield  from  TOO  Gm  of 
solution  can  not  be  over  42.46  Gm. 


396  IRON  CITRATE. 

Description. — The  solution  of  ferric  citrate  of  the  American 
Pharmacopoeia  is  dark  brown-red,  odorless,  and  has  a  slightly 
ferruginous  and  only  faintly  acid  taste.  Its  reaction  on  test-paper 
is  acid.  The  sp.  w.  is  not  less  than  1.250  at  15°. 


IRON    CITRATE    WITH    QUININE. 

FERRI    ET    QUININAE    CITRAS  ;    U.    S. 

Ferric  citrate 22  parts 

Quinine,   dried  at   100°   C.   until   it  ceases 

to  lose  weight 3  parts 

Dissolve  the  ferric  citrate  in  30  parts  of  distilled  water  in  a 
porcelain  dish  over  a  water-bath  at  not  over  60°  C.  Add  the 
alkaloid  and  stir  constantly  until  dissolved.  Evaporate  at  the 
temperature  named  until  the  liquid  is  reduced  to  the  consistence 
of  syrup,  and  spread  it  on  glass  plates  to  dry  in  scales. 

Keep  the  product  in  well  stoppered  bottles,  in  a  cool,  dark 
place. 

Notes.  This,  the  official  citrate  of  iron  and  quinine  of  the 
United  States,  is  reddish  brown  and  only  slowly,  though  per- 
fectly, water  soluble.  The  most  commonly  employed  citrate  of 
iron  and  quinine,  however,  is  that  prepared  with  the  addition  of 
ammonia,  by  which  the  preparation  is  not  only  rendered  more 
readily  soluble  but  changed  also  in  color,  being  greenish  yellow. 

The  quinine  should  be  finely  divided,  and  ought  to  be  tritur- 
ated first  with  five  parts  of  water  and  then  with  a  portion  of  cold 
solution  of  the  citrate  of  iron,  being  afterwards  well  mixed  with 
the  whole  before  the  digestion  begins.  Otherwise  it  may  run 
together  in  lumps,  which,  afterwards,  are  very  difficult  to  dis- 
solve. 

In  this,  as  in  all  other  scale  salts  of  iron,  it  is  necessary  that  no 
considerable  excess  of  free  citric  acid  should  be  contained  in  the 
preparation,  for  then  the  salt  will  not  form  scales,  but  adheres 
like  a  varnish  to  the  glass  plates. 

"Quinine  dried  at  100°  C.,  until  it  ceases  to  lose  weight,"  is 
monohydrated  quinine  (C20H24N2O2.H2O).  The  drying  at  this 
temperature  is  directed  for  the  purpose  of  insuring  uniformity. 


IRON   CITRATE.  397 

Description. — Transparent  scales,  reddish  to  yellowish  brown, 
slowly  hygroscopic  on  exposure  to  moist  air,  odorless,  having  a 
bitter  and  mildly  ferruginous  taste,  and  slightly  acid  reaction. 
Slowly  but  wholly  soluble  in  cold  water,  more  readily  so  in  hot 
water,  and  but  partially  soluble  in  alcohol. 

Its  solubility  is  impaired  by  age.  It  contains  12  per  cent  of 
mono-hydrated  quinine. 

German  Preparation. 

Citric  acid 6  parts 

Powdered   iron 3  parts 

Quinine    i  part 

Dissolve  the  citric  acid  in  500  parts  of  water,  heated  in  a  por- 
celain dish ;  add  the  iron  and  digest  over  a  water-bath,  with  fre- 
quent stirring,  for  48  hours,  or  until  the  liquid  acquires  a  red- 
dish-brown color.  Filter.  Evaporate  the  filtrate  to  50  parts, 
and  then  add  the  quinine  previously  triturated  with  a  portion  of 
the  liquid.  When  the  alkaloid  has  dissolved,  evaporate  to  a 
syrupy  consistence  and  spread  it  on  glass  plates  to  dry  in  scales. 

Notes.  This  preparation  contains  both  ferrous  and  ferric  cit- 
rate. The  quinine  should  be  recently  precipitated  from  a  solu- 
tion of  1.3  parts  of  quinine  sulphate,  dissolved  in  water  with  the 
aid  of  dilute  sulphuric  acid,  the  precipitant  being  sodium  hydrox- 
ide. 

Description. — Dull  red-brown  scales  ;  odorless  ;  bitter,  ferrugin- 
ous. Slowly  but  completely  soluble  in  water.  Contains  from  9 
to  10  per  cent  of  quinine. 

Swedish  Preparation. 

The  working  formula  of  the  Swedish  Pharmacopoeia  is  as  fol- 
lows : 

Citric  acid 13  parts 

Ferric   chloride 12  parts 

Quinine   3  parts 

Ammonia   water 57  parts 

Dissolve  the  ferric  chloride  in  400  parts  of  cold  water,  and  pour 
the  solution  into  a  mixture  of  the  ammonia  water  and  60  parts 


398  IRON   CITRATE. 

of  water.  Wash  the  ferric  hydroxide  thoroughly,  and  press  out 
the  moisture  from  it.  Dissolve  the  citric  acid  in  25  parts  of  dis- 
tilled water,  warm  the  solution  over  a  water-bath  at  not  above 
40°  C.  (104°  F.),  and  add,  during  constant  stirring,  the  ferric 
hydroxide  in  small  portions  at  a  time  until  the  citric  acid  is  sat- 
urated. Then  add  the  quinine  in  the  manner  prescribed  in  the 
working  formula  for  the  preparation  of  the  "Iron  and  Quinine 
Citrate"  of  the  American  Pharmacopoeia. 

Description. — Similar  to  the  preparation  of  the  American  Phar- 
macopoeia. 

It  contains  about  14  per  cent  of  quinine. 

The  Norwegian  and  Danish  Pharmacopoeias  require  from  10 
to  12  per  cent  of  quinine. 

Soluble  Citrate  of  Iron  and  Quinine. 

FERRI    ET    QUININAE    CITRAS    SOLUBILIS ;    U.    S. 

Ferric   citrate 85  Gm 

Quinine,   dried  at   100°   C.  to    a    constant 

weight 12  Gm 

Citric   acid 3  Gm 

Ammonia  water. 

Distilled  water,  each  sufficient. 

Heat  160  ml  of  distilled  water  in  a  porcelain  dish  over  a  water- 
bath  to  a  temperature  not  exceeding  60°  C.,  and  add  the  ferric 
citrate,  stirring  until  the  scale-salt  is  dissolved.  Triturate  the 
quinine  and  the  citric  acid  with  20  ml  of  distilled  water,  add  this 
to  the  solution  of  ferric  citrate  in  the  porcelain  dish,  and  stir  con- 
stantly until  all  is  dissolved.  Now  add  gradually  and  with  con- 
stant stirring  about  50  ml  of  ammonia  water,  or  a  sufficient  quan- 
tity to  render  the  solution  greenish-yellow,  waiting  after  each 
addition  of  ammonia  until  the  precipitated  quinine  shall  have  re- 
dissolved  before  another  portion  of  the  ammonia  water  is  added. 
Evaporate  the  greenish-yellow  solution  over  a  water  bath,  at  a 
temperature  not  exceeding  60°  C.  to  a  syrupy  consistence  and 
spread  it  on  plates  of  glass  or  porcelain  to  dry  in  scales. 

Keep  the  product  in  well-stoppered  bottles  protected  from 
light. 

Description. — Thin,  transparent  scales  of  a  greenish  golden- 


IRON   CITRATE.  399 

yellow  color;  odorless;  taste  bitter,  mildly  ferruginous.  Com- 
pletely and  quickly  soluble  in  water.  Only  partially  soluble  in 
alcohol.  Darkens  on  exposure  to  light.  Hygroscopic  in  damp 
air. 

It  contains  12  per  cent  of  monohydrated  quinine. 

British  Preparation. 

Solution  of  normal  ferric  sulphate,  U.  S.  .   328  ml 

Sulphate  of  quinine 40  Gm 

Diluted  sulphuric  acid 60  ml 

Citric   acid. 123  Grrt 

Ammonia  water,  distilled  water,  each  sufficient. 

Mix  320  ml  of  ammonia  water  with  1600  ml  of  cold  water ;  add 
to  this  the  solution  of  ferric  sulphate,  also  previously  diluted  with 
1600  ml  of  cold  water,  stirring  constantly  and  briskly.  Let  the 
mixture  stand  for  two  hours,  stirring  it  occasionally ;  then  trans- 
fer it  to  a  wetted  muslin  strainer,  and  when  thoroughly  drained, 
wash  the  hydroxide  with  water  until  the  washings  cease  to  give  a 
precipitate  with  barium  chloride. 

Mix  the  quinine  sulphate  with  320  ml  of  water,  add  the  di- 
luted sulphuric  acid,  and,  when  the  salt  is  dissolved,  precipitate 
the  quinine  with  a  slight  excess  of  ammonia  water.  Collect  the 
precipitate  on  a  filter,  and  wash  it  with  1000  ml  of  distilled  water. 

Dissolve  the  citric  acid  in  125  ml  of  distilled  water,  heated  on 
a  water-bath ;  add  the  ferric  hydroxide,  previously  well  drained ; 
stir  them  together,  and,  when  the  hydroxide  has  dissolved,  add  the 
precipitated  quinine,  continuing  the  stirring  until  the  alkaloid 
has  also  dissolved.  Let  the  mixture  cool.  Add  cautiously,  a 
little  at  a  time,  60  ml  of  ammonia  water  previously  diluted  with 
80  ml  of  distilled  water,  stirring  briskly,  and  allowing  the  quinine 
which  separates  with  each  addition  of  ammonia  to  re-dissolve  be- 
fore adding  another  portion.  Filter  the  solution,  evaporate  it  to 
the  consistence  of  a  thin  syrup,  and  spread  it  on  glass  plates  to 
dry  in  scales  at  not  over  40°  C. 

Notes.  The  product  is  in  greenish  golden  yellow  scales,  some- 
what hygroscopic,  and  readily  soluble  in  water.  It  contains  about 
16  per  cent  of  quinine. 


4OO  IRON   CITRATE. 

Solution  of  Citrate  of  Iron  and  Quinine. 

Ammonio-f erric  citrate 65  parts 

Quinine,  dried  at   100°   C.  until  it  ceases 

to  lose  weight. . 12  parts 

Citric  acid 28  parts 

Alcohol    30  parts 

Dissolve  the  citrate  of  iron  and  ammonium  in  200  parts  of 
distilled  water,  in  a  tared  porcelain  dish;  heat  the  solution  over 
a  water-bath  to  60°  C.,  add  the  citric  acid,  and,  when  this  has 
dissolved,  add  the  alkaloid  previously  triturated  to  a  homogene- 
ous mixture  with  a  cooled  portion  of  the  liquid,  and  continue 
stirring  until  a  perfect  solution  results.  Evaporate  to  160  parts, 
let  cool,  add  the  alcohol,  and  finally  10  parts  of  distilled  water. 

Should  be  kept  in  a  well  stoppered  bottle,  in  a  cool,  dark  place. 

Description. — A  dark  greenish-yellow  to  yellowish-brown 
liquid.  Odorless.  Taste  like  that  of  citrate  of  iron  and  quinine. 
Reaction  slightly  acid.  Corresponds  to  about  50  per  cent  of 
soluble  citrate  of  iron  and  quinine. 

IRON    CITRATE    WITH    STRYCHNINE. 

FERRI    ET    STRYCHNIN AE    CITRAS. 

Citrate  of  iron  and  ammonium 98  parts 

Strychnine    I  part 

Citric   acid I  part 

Dissolve  the  ammonio-ferric  citrate  in  100  parts  of  distilled 
water;  and  the  alkaloid,  together  with  the  citric  acid,  in  20  parts 
of  distilled  water.  Mix.  Evaporate  the  mixture  by  water-bath 
at  not  over  60°  C.  to  a  syrupy  liquid,  and  spread  this  on  glass 
plates  to  dry  in  scales. 

Keep  the  product  in  well  stoppered  bottles,  in  a  cool,  dark 
place. 

Description. — Transparent,  garnet-red  scales,  deliquescent  on 
exposure  to  air,  odorless,  having  a  bitter  and  slightly  ferruginous 
taste,  and  a  slightly  acid  reaction.  Readily  and  wholly  soluble  in 
water. 


IRON   NITRATE.  40 1 

IRON  (FERRIC)   NITRATE    SOLUTION. 

LIQUOR    FERRI    NITRATIS. 

An  aqueous  solution  of  ferric  nitrate  [Fe(NO3);,^242],  con- 
taining about  6.2  per  cent  of  the  anhydrous  salt,  and  correspond- 
ing to  about  1.4  per  cent  of  metallic  iron. 

Solution  of  ferric  sulphate 18  parts 

Ammonia    water 15  parts 

Nitric   acid 71  parts 

Distilled  water. 
Water. 

Mix  the  ammonia  water  with  50  parts  of  cold  water,  and  the 
solution  of  ferric  sulphate  with  150  parts  of  cold  water.  Add 
the  latter  solution  slowly  to  the  diluted  ammonia  water,  with 
constant  stirring.  Let  the  mixture  stand  until  the  precipitate 
has  subsided  as  far  as  practicable,  and  then  decant  the  supernatant 
liquid.  Add  to  the  precipitate  100  parts  of  cold  water,  mix  well, 
and  again  set  the  mixture  aside,  as  before.  Repeat  the  washing 
with  successive  portions  of  cold  water,  in  the  same  manner,  until 
the  washings  produce  but  a  slight  cloudiness  with  barium  chloride 
test-solution.  Pour  the  washed  ferric  hydroxide  on  a  wet  muslin 
strainer,  and  let  it  drain  thoroughly.  Then  transfer  it  to  a  porce- 
lain capsule,  add  the  nitric  acid,  and  stir  with  a  glass  rod,  until  a 
clear  solution  is  obtained.  Finally,  add  enough  distilled  water  to 
make  the  finished  product  weight  100  parts.  Filter,  if  necessary. 

Reactions.  Fe2(SO4).,+6H4NOH=2Fe(OH)3+3(H4N)2SO4; 
then,  Fe(OH)8+3HNO,=Fe(N03)3+3H,0. 

Description, — A  clear,  amber-colored  or  reddish  liquid ;  odor- 
less; taste  acid  and  styptic.  Reaction  acid.  Sp.  w.  1.050  at  15°. 

The  solution  of  ferric  nitrate  of  the  British  Pharmacopoeia  is 
more  than  twice  as  strong,  containing  about  3.01  per  cent  of  iron. 
But  the  British  formula  employs  an  amount  of  nitric  acid  which 
corresponds  to  only  135  parts  of  absolute  HNO;!  for  each  1000 
parts  of  finished  solution,  while  the  American  formula  employs 
nitric  acid  corresponding  to  102  parts  of  absolute  HNO3  for  each 
1000  parts,  so  that  while  the  British  preparation  contains  more 

Vol.   11—26 


4<D2  IRON    NITRATE. 

than  twice  as  much  iron  it  uses  only  33  per  cent  more  nitric  acid. 
Hence  the  British  preparation  contains  both  ferrous  and  ferric 
nitrate,  while  the  American  preparation  contains  only  ferric  ni- 
trate. 

The  British  Formula  ( 1898) 
is  as  follows : 

Iron    20      Gm 

Nitric  acid  (70%  of  HNO3),  90  ml,  or.  .    127.8  Gm 
Distilled  water. 

Dilute  the  nitric  acid  with  320  ml  of  distilled  water.  Dissolve 
the  iron  in  the  mixture,  being  careful  to  moderate  the  reaction, 
should  it  become  too  violent,  by  the  addition  of  a  little  more  dis- 
tilled water.  Filter.  Add  enough  distilled  water  to  produce  600 
ml  of  the  solution  (or  664.2  Gm). 

This  solution  has  the  sp.  w.  1.107. 


IRON  OXYCHLORIDE  SOLUTION. 

LIQUOR     FERRI     OXYCHLORIDI. 

The  following  process  is  after  the  Swiss  Pharmacopoeia  ( 1893)  : 

Solution  of  ferric  chloride,  U.  S 300  parts 

Ammonia  water 400  parts 

Hydrochloric  acid  27  parts 

Distilled  water,  sufficient. 

Warm  the  solution  of  ferric  chloride  to  about  30°  C.  Dilute 
300  parts  of  ammonia  water  with  300  parts  of  water.  Add  the 
ammoniacal  liquid  slowly  and  with  constant  stirring  to  the  solu- 
tion of  ferric  chloride.  Then  dilute  the  mixture  with  1000  parts 
of  distilled  water. 

Dilute  100  parts  of  ammonia  water  with  2000  parts  of  distilled 
water. 

Now  pour  the  iron  mixture  and  the  diluted  ammonia,  simul- 
taneously, slowly,  and  with  uninterrupted  stirring,  into  8000  parts 
of  distilled  water. 

Wash  the  precipitate  by  the  affusion  and  decantation  of  distilled 
water  until  the  washings  no  longer  give  any  reaction  for  chloride. 

Collect  the  washed  precipitate  on  a  strainer  and  express  the 


IRON  OXYCHLORIDE.  403 

water  from  it  by  strong  pressure  until  the  press  cake  is  reduced  to 
a  weight  not  exceeding  400  parts. 

Transfer  this  to  a  bottle,  add  the  hydrochloric  acid,  and  also 
enough  distilled  water  to  make  the  total  weight  of  the  mixture 
looo  parts. 

Let  the  mixture  stand,  shaking  it  occasionally,  until  the  solid 
matter  has  dissolved. 

Filter  the  solution. 

The  finished  product  should  have  the  sp.  w.  1.05. 

Keep  the  product  in  a  dark  place,  or  in  amber-colored  bottles. 

Description. — A  clear  brown-red  liquid,  containing  an  amount 
of  ferric  oxychloride  corresponding  to  about  3.5  per  cent  of  Fe. 
It  should  yield  5  per  cent  of  ferric  oxide  on  precipitation  with 
ammonia  in  excess  and  ignition  of  the  precipitate  in  the  usual  way. 

Dialysed  Solution  of  Iron. 

LIQUOR    FERRI    DIALYSATUS. 

Solution  of  ferric  chloride 100  ml 

Ammonia  water 165  ml 

Distilled  water,  sufficient. 

Mix  86  ml  of  the  solution  of  ferric  chloride  with  500  ml  of 
cold  distilled  water.  Pour  the  mixture  slowly  and  with  constant 
stirring  into  the  ammonia  water  previously  diluted  with  400  ml 
of  cold  distilled  water.  Wash  the  precipitate  with  cold  distilled 
water  first  by  decantation  and  afterwards  on  a  wetted  muslin 
strainer  until  the  washings  cease  to  be  affected  by  test-solution.of 
silver  nitrate  acidulated  with  nitric  acid.  Let  drain,  and  then 
press  out  from  the  magma  as  much  as  possible  of  the  moisture  it 
holds. 

Add  the  ferric  hydroxide  to  the  remainder  of  the  solution  of 
ferric  chloride,  stir  well,  and  set  aside  until  no  more  ferric  hy- 
droxide dissolves. 

Decant  the  liquid  from  the  undissolved  portion,  place  it  in  a 
covered  dialyser,  and  wash  it  by  dialysis  until  the  washings  are 
nearly  tasteless. 

Then  dilute  the  solution  in  the  dialyser  until  it  measures  nearly 
375  ml,  and  has  a  sp.  gr.  of  1.047. 


404  IRON  PEPTONATE. 

Keep  the  product  in  tightly  closed  bottles  and  protected  against 
light. 

Notes.  When  10  Gm  of  this  solution  is  treated  with  ammonia 
water  in  excess,  the  precipitate,  when  washed,  dried,  and  ignited, 
should  weigh  0.50  Gm  .  A  drop  of  the  solution,  diluted  with 
water,  should  yield  no  precipitate  with  test-solution  of  silver 
nitrate  acidulated  with  nitric'  acid. 

This  is  the  so-called  "dialysed  iron."  It  will  be  observed  that 
the  product  is  not  the  dialysed  portion,  but  the  residue  after  the 
dialysis.  It  contains  a  highly  basic  ferric  oxychloride. 

Description. — A  dark  reddish-brown  liquid;  odorless,  and  of  a 
mild,  non-styptic  taste. 


IRON    PEPTONATE. 

FERRUM     PEPTONATUM. 

Solution  of  oxychloride  of  iron  (contain- 
ing 3.5  per  cent  of  Fe) 240  parts 

Dried  egg  albumen 20  parts 

Hydrochloric  acid  (25%  of  HC1) 34  parts 

Pepsin    I  part 

Distilled  water,  sufficient. 

Dissolve  the  egg  albumen  in  2000  parts  of  distilled  water,  to 
which  have  been  previously  added  the  pepsin  together  with  30 
parts  of  the  hydrochloric  acid.  Let  this  mixture  stand,  stirring 
or  shaking  it  occasionally,  for  a  period  of  12  hours  in  a  place 
where  the  temperature  is  about  40°  C.  Then  let  the  solution  cool 
to  20°  C.,  filter  or  strain  it,  and  carefully  neutralize  it  with  a  very 
weak  solution  of  sodium  hydroxide.  Should  a  precipitate  be 
formed,  filter  the  liquid. 

Dilute  the  solution  of  ferric  oxychloride  with  2000  parts  of 
distilled  water,  and  add  this  solution  to  the  solution  of  digested 
egg  albumen.  Mix  well. 

Neutralize  the  mixture  carefully  with  a  very  weak  solution  of 
sodium  hydroxide,  stirring  well. 

Wash  the  precipitated  iron  peptonate  with  distilled  water  as 
long  as  the  washings  give  a  precipitate  with  silver  nitrate  solu- 


IRON  PEPTONATE.  405 

tion.  [The  washing  should  not  be  continued  while  mere  opales- 
cence  is  caused  by  the  silver  solution.] 

Collect  the  precipitate  on  a  cloth  strainer,  let  it  drain  well,  trans- 
fer it  to  a  porcelain  dish,  add  the  remaining  3  parts  of  the  hydro- 
chloric acid,  and  heat  the  mixture  carefully  over  a  water-bath,  at 
not  over  56°  C,  until  solution  is  effected. 

Evaporate  the  liquid  at  not  above  50°  C.  to  the  consistence  of 
syrup,  spread  the  thick  liquid  upon  glass  plates,  and  let  it  dry  in 
scales. 

Description. — Red-brown  scales,  odorless,  and  of  feebly  bit- 
terish ferruginous  taste.  Forms  a  clear  solution  with  water.  The 
solution  has  an  acid  reaction.  It  should  not  become  turbid  on 
heating  above  60°  C.  or  on  addition  of  alcohol  (absence  of  albu- 
men). 

Solution  of  Iron  Peptonate 

may  be  prepared  by  mixing  the  still  moist  iron  peptonate  made 
from  20  parts  of  dry  egg  albumen  with  1780  parts  of  distilled 
water  and  200  parts  of  brandy. 
Should  be  protected  against  light. 

Solution  of  Iron  and  Manganese  Peptonate. 

1.  Make  a  solution  of  10  parts  of  citric  acid  in  50  parts  of  dis- 
tilled water,  and  add  enough  ammonia  water  (24.2  parts)  to  make 
normal  ammonium  citrate. 

2.  Dissolve  3.7  parts  of  manganous  chloride  in  10  parts  of 
distilled  water. 

3.  Dissolve  24  parts  of  iron  peptonate  in  300  parts  of  distilled 
water. 

4.  Mix  150  parts  of  alcohol  with  400  parts  of  distilled  water. 
Add  solution  i  to  2.    Then  add  3.    Then  4.    Finally  add  enough 

distilled  water  to  make  the  total  product  weigh  1000  parts. 

Notes.  This  preparation  is  usually  flavored  with  aromatic  tinc- 
ture (Swiss  Ph.),  and  the  tinctures  of  cinnamon  and  vanilla,  to- 
gether with  some  acetic  ether. 

Must  be  protected  against  light. 

Should  it  become  unclear  it  may  be  rendered  clear  again  by 
gently  warming  it,  and  then  adding  a  few  drops  of  ammonia 
water. 


406  IRON  TARTRATE. 

IRON  AMMONIUM   TARTRATE. 

FERRI    ET    AMMONII    TARTRAS. 

( Ferryl-Ammonium  Tartrate.) 

Solution  of  normal  ferric  sulphate 90  parts 

Tartaric  acid 18  parts 

Ammonia  water 72  parts 

Ammonia  water,  distilled  water,  each  sufficient. 

Mix  the  ammonia  water  with  180  parts  of  cold  water;  add 
gradually,  and  with  constant  stirring,  the  solution  of  tersulphate 
of  iron  previously  diluted  with  900  parts  of  cold  water. 

Pour  the  mixture  on  a  wetted  muslin  strainer,  allow  the  magma 
to  drain,  and  then  return  it  to  the  precipitation  vessel  and  mix  it 
well  with  1000  parts  of  cold  water.  Drain  it  again  on  the  strainer, 
and  repeat  the  operation  once,  or  oftener,  until  the  washings  only 
give  a  slight  cloudiness  with  barium  chloride  solution.  Then 
allow  it  to  drain  thoroughly.  Dissolve  one-half  of  the  tartaric 
acid  in  45  parts  of  distilled  water,  neutralize  the  acid  exactly  with 
ammonia  water,  then  add  the  remainder  of  the  tartaric  acid,  and 
dissolve  it  by  the  aid  of  heat.  Keep  the  solution  of  ammonium 
bitartrate  hot,  but  not  above  60°  C,  over  a  water-bath,  and  add 
to  it,  with  constant  stirring,  the  ferric  hydroxide,  in  small  portions 
at  a  time,  until  no  more  will  dissolve.  Filter  the  solution  while 
hot,  evaporate  it  at  not  over  60°  C.  to  the  consistence  of  syrup, 
and  spread  it  on  glass  plates  to  dry  in  scales. 

Keep  the  product  in  amber-colored  bottles,  tightly  corked,  and 
put  in  a  cool,  dark  place. 

Notes.  The  remarks  under  Iron  and  Potassium  Tartrate  ap- 
ply in  a  general  way  to  this  process  as  well.  The  ammonium 
bitartrate  is  H4NHC4H4O6,  by  which  the  ferric  hydroxide  is  dis- 
solved in  a  manner  analogous  to  the  solution  effected  by  digesting 
the  hydroxide  with  potassium  bitartrate  in  making  the  tartrate  of 
iron  and  potassium. 

Description. — Transparent,  garnet-red  to  brown-red  scales, 
somewhat  lighter  and  clearer  in  color  than  the  tartrate  of  iron  and 
potassium.  Odorless.  Taste  sweetish,  slightly  ferruginous.  Very 


IRON  TARTRATE.  407 

soluble  in  water.    Insoluble  in  alcohol.     Produces  more  clear  and 
permanent  solutions  than  potassium  iron  tartrate. 

IRON   POTASSIUM   TARTRATE. 

FERRI    ET  POTASSII  TARTRAS. 

(Ferryl-Potassium  Tartrate.) 

Solution  of  normal  ferric  sulphate 12  parts 

Potassium  bitartrate   4  parts 

Distilled  water. 
Ammonia  wrater,  sufficient. 

Mix  10  parts  of  ammonia  water  with  20  parts  of  cold  water; 
add  gradually,  and  with  constant  stirring,  the  solution  of  tersul- 
phate  of  iron,  previously  diluted  with  100  parts  of  cold  water. 
Pour  the  mixture  on  a  wet  muslin  strainer,  allow  the  magma  to 
drain,  and  then  return  it  to  the  precipitation  vessel  and  mix  it  well 
with  100  parts  of  cold  water.  Drain  it  again  on  the  strainer,  and 
repeat  this  operation  once  or  twice,  as  may  be  necessary,  until 
the  washings  produce  but  a  slight  cloudiness  with  test-solution  of 
barium  chloride.  Let  the  magma  be  well  drained;  then  forcibly 
press  out  of  it  as  much  of  the  water  as  possible.  Add  it  in  small 
portions  at  a  time  to  a  mixture  of  the  distilled  water  and  the  potas- 
sium bitartrate,  heated  over  a  water-bath  at  not  over  60°  C, 
stirring  constantly  until  all  the  ferric  hydroxide  has  been  added 
and  dissolved.  Filter  while  hot  and  set  the  filtrate  aside  in  a  cool, 
dark  place  for  twenty-four  hours  ;  then  stir  it  well  with  a  'porcelain 
or  glass  stirrer  until  any  precipitate  which  may  have  formed  in 
the  liquid  is  evenly  distributed  through  it.  Then  cautiously  add 
just  enough  ammonia  water  to  dissolve  this  precipitate,  filter,  and 
evaporate  the  solution  in  a  porcelain  dish  to  the  consistence  of 
thick  syrup,  and  spread  it  on  glass  plates  to  dry  in  scales. 

Keep  the  product  in  well  corked  amber  bottles,  in  a  dark  place. 

Reaction.  Ferric  hydroxide  is  first  prepared  from  the  ferric  sul- 
phate : 

Fe2  ( S04)  8+6H4NOH=Fe2  (OH)  6+3  ( H4N)  2SO4. 

The  ferric  hydroxide  is  then  dissolved  by  the  potassium  tartrate, 
forming  several  compounds,  one  of  which  is  perhaps : 


408  IRON  TARTRATE. 

3KHC4H406+Fe  ( OH )  3=K3Fe  ( C4H4O6 )  3+3H2O, 
while  another  is  probably  made  in  this  way : 

KHC4H4O6+Fe(OH)3=K(FeO)C4H4O6+2H2O. 

But  the  tartrate  of  iron  and  potassium  probably  is  not  a  definite 
double  salt ;  the  pharmacopoeial  products  are  all  variable  as  to  the 
proportion  of  iron. 

Notes.  Whether  prepared  from  solution  of  tersulphate  of  iron 
or  from  solution  of  chloride  of  iron,  the  ferric  hydroxide  must  be 
carefully  precipitated,  from  cold  dilute  solutions,  and  well  washed. 
When  made  from  chloride  it  is  more  readily  washed  clean.  The 
hydroxide  does  not  dissolve  rapidly  in  the  liquid,  or  the  soluble  tar- 
trate of  iron  and  potassium  is  but  slowly  formed  from  the  ferric 
hydroxide  and  the  potassium  bitartrate.  Several  hours  are  required 
to  complete  the  solution.  In  view  of  the  fact  that  ferric 
hydroxide  is  so  liable  to  become  basic  and  insoluble  when 
subjected  to  heat,  it  is  best  to  add  the  ferric  hydroxide 
in  portions,  to  regulate  the  heat  carefully  and  to  stir 
constantly.  The  success  of  the  whole  process  depends  to  a  great 
extent  upon  the  character  of  the  ferric  hydroxide  and  upon  the  pre- 
cautions described  in  the  foregoing.  The  addition  of  ammonia 
is  intended  to  render  the  product  readily  water  soluble  without 
residue.  The  Pharmacopoeia  does  not  direct  that  the  solution 
should  be  filtered,  but  this  is  necessary  to  obtain  a  good  product. 

Description. — Transparent  garnet-red  or  brown-red  scales,  odor- 
less, taste  sweetish,  slightly  ferruginous.  Very  soluble  in  water; 
insoluble  in  alcohol. 

Impure  Malate  of  Iron. 

Iron  wire,  cut 20  Gm 

Crab  apples,  nearly  ripe 500  Gm 

Pare  the  apples,  beat  them  into  a  pulp,  and  express  the  juice. 
Add  the  iron,  mix  well,  set  the  mixture  in  a  warm  place  for  ten 
days,  or  until  all  signs  of  effervescence  cease,  stirring  frequently. 
Replace  from  time  to  time  the  water  lost  by  evaporation.  Heat 
the  mixture  on  a  water-bath  at  70°  C.  for  six  hours,  replacing 
water  lost  by  evaporation.  Add  100  ml  of  warm  water,  express, 


IRON    FERROCYANIDE.  409 

mix  the  residue  with  another  100  ml  of  warm  water,  and  express 
a^ain.  Mix  the  liquids  and  set  the  mixture  aside  in  a  cool  place 
to  settle.  Decant  the  clear  liquid,  or  filter  if  necessary,  and  evap- 
orate to  a  thick  extract. 

The  product  is  greenish  black,  has  a  styptic  taste,  yields  a  clear 
solution  with  water,  and  usually  contains  about  7  to  8  per  cent  of 
iron. 

Note.  Any  sour  apples  may  be  used  if  wild  apples  are  not  avail- 
able. This  preparation  is  still  retained  in  several  pharmacopoeias, 
and  tinctures  are  made  from  it. 

Description.— A  dark  brown-red  (nearly  black)  extract-like 
mass. 

IRON  (FERRIC)  FERROCYANIDE. 

FERRI     FERROCYANIDUM. 

(Prussian  Blue.) 
Fe4(FeCye)  3=860. 

Solution  of  ferric  chloride,  U.  S.  P 23  ml 

Potassium  ferrocyanide 14  Gm 

Distilled  water,  sufficient. 

Dilute  the  solution  of  ferric  chloride  with  450  ml  of  distilled 
water.  Dissolve  the  potassium  ferrocyanide  in  300  ml  of  distilled 
water.  Filter  both  liquids.  Add  the  solution  of  potassium  ferro- 
cyanide slowly  and  with  constant  stirring,  to  the  solution  of  chlor- 
ide of  iron.  Let  the  precipitate  settle,  and  wash  it  first  by  decan- 
tation,  changing  the  wash  water  as  frequently  as  practicable ;  then 
transfer  the  magma  to  a  wetted  muslin  strainer  and  continue  the 
washing  until  the  washings  are  tasteless.  Let  drain,  and  dry  it 
on  the  muslin,  spread  in  a  thin  layer.  If  necessary,  finish  the  dry- 
ing on  glass  plates  in  the  drying  chamber.  Reduce  the  product 
to  a  fine  powder. 

Reaction.    3K4FeCy6+4FeCl.,==i2KCl+Fe4(FeCyG)3. 

Notes.  The  dilute  condition  of  the  solutions  is  necessary  because 
the  precipitate  is  very  voluminous.  It  is  also  necessary  that  the 
ferric  chloride  should  be  in  excess  over  the  potassium  ferrocyanide 


410  IRON  HYDROXIDE. 

throughout  the  reaction,  that  for  this  purpose  the  cyanide  should 
be  added  to  the  chloride  and  not  vice  versa,  and  that  some  ferric 
chloride  should  remain  undecomposed  at  the  end.  Otherwise  the 
product  will  be  contaminated  with  more  potassium  salt  than  when 
the  directions  given  are  observed.  Under  any  circumstances  there 
will  be  a  slight  amount  of  potassium  compound  in  the  product. 
Any  attempt  to  wash  out  all  the  potassium  salt  will  result  in  the 
formation  of  ferric  oxide,  which  remains  in  the  preparation. 

The  precipitate  is  a  voluminous  magma  which  is  difficult  to 
wash,  as  it  settles  very  slowly.  Washing  on  a  filter  is  impracti- 
cable, because  the  precipitate  completely  closes  the  pores  of  the 
paper. 

The  presence  of  a  little  free  HC1  in  the  liquid  (which  will  be 
insured  by  using  the  solution  of  ferric  chloride  of  the  U.  S.  P.) 
considerably  facilitates  the  washing. 


IRON  (FERRIC)  HYDROXIDE. 

FERRI     HYDROXIDUM. 

Fe(OH)3=io;. 

Solution  of  normal  ferric  sulphate  ( 50  Gm, 

or)    38  ml 

Ammonia  water  (40  Gm,  or) 42  ml 

Water,  sufficient. 

Dilute  the  ammonia  water  with  100  ml  of  cold  water  in  a  pre- 
cipitation vessel  of  about  one  liter's  capacity.  Dilute  the  solution 
of  ferric  sulphate  with  500  ml  of  cold  water,  and  pour  this  into 
the  dilute  ammonia  slowly  and  during  constant  stirring. 

Wash  the  precipitated  ferric  hydroxide  with  cold  water,  first  by 
affusion  and  decantation,  and  afterwards  on  a  wetted  muslin 
strainer,  until  the  washings  are  tasteless.  Then  let  the  magma 
drain,  return  it  to  the  precipitation  vessel,  and  mix  it  well  with  as 
much  cold  water  as  the  vessel  will  hold,  or  about  one  liter.  Let 
settle,  decant  the  supernatant  liquid,  and  again  transfer  the  magma 
to  the  wetted  strainer  and  allow  it  to  drain.  Continue  the  wash- 
ing in  this  manner  until  the  wash  water  is  no  longer  affected  by 
test-solution  of  barium  chloride. 

[When  the  ferric  hydroxide  is  to  be  used  as  an  antidote  for 


IRON  HYDROXIDE.  411 

arsenic,  the  whole  process  must  be  hastened,  and  the  washing  need 
not  be  carried  farther  than  to  remove  the  mother  liquor.  To  effect 
this  the  precipitate  is  allowed  to  drain  until  most  of  the  liquid  has 
run  off,  and  the  strainer  is  then  gathered  up  so  as  to  enclose  the 
magma,  which  is  then  forcibly  pressed  with  the  hands  until  no 
more  liquid  can  be  squeezed  out,  after  which  enough  water  is 
added  to  the  hydroxide  to  make  the  weight  of  the  whole  product 
equal  to  twice  the  weight  of  the  solution  of  ferric  sulphate  used.] 

Reaction.    Fe2(SO4)3+6H4NOH=2Fe(OH)3+3(H4N)2SO4. 

Notes.     Dilute  and  cold  solutions  are  necessary.     The  diluted 
solution  of  ferric  sulphate  should  be  poured  slowly,  or  in  a  jsmall  \ 
stream,  into  the  diluted  ammonia  water  during  constant  stirring,  ! 
as  directed.    When  the  whole  of  the  iron  solution  has  been  added,   j 
the  mixture  should  still  have  a  decidedly  ammoniacal  odor; 'as 
the  ammonia  gas  is  diffused  through  the  stratum  of  air  above  the 
surface  of  the  liquid,  that  air  must  be  fanned  or  blown  away  before 
the  odor  of  the  liquid  itself  can  be  ascertained. 

There  are  several  ferric  hydroxides,  differing  from  each  other  in 
the  proportions  of  HO  they  contain,  in  color,  and  in  their  solubility 
in  acids.  The  product  intended  by  the  Pharmacopoeia  is  Fe(OH)3 ; 
another  ferric  hydroxide  is  Fe2O(OH)4;  and  dried  ferric  hydrox- 
ide is  OFe(OH).  The  more  basic  it  is,  and  the  less  water  it 
contains,  the  less  readily  soluble  is  it.  As  obtained  by  the  official 
process,  all  the  necessary  precautions  being  observed,  the  product 
is  dark  reddish-brown  and  readily  soluble  in  citric  acid,  and  in 
glacial  acetic  acid.  When  yellowish-brown,  brown,  grayish- 
brown,  or  clay-colored,  it  is  basic,  insoluble  and  unfit  for  the  uses 
for  which  it  is  intended  in  pharmacy. 

The  solution  of  ferric  sulphate  must  contain  the  full  amount  of 
ferric  sulphate,  and  be  free  from  ferrous  salt  in  order  that  the 
quantity  of  ferric  hydroxide  obtained  from  it  may  be  definite; 
the  importance  of  this  will  be  readily  understood  from  the  fact* 
that  the  proportions  of  the  materials  prescribed  in  several  working 
formulas  for  ferric  salts  are  calculated  with  reference  to  the 
amount  of  ferric  hydroxide  theoretically  yielded  by  the  solution 
of  ferric  sulphate. 

In  summer  it  is  best  to  use  ice  for  cooling  the  dilute  solutions 
previous  to  the  precipitation.  The  chemical  reaction  generates 
heat,  and  if  the  solutions  are  already  warm  the  temperature  of 


412  IRON  HYDROXIDE. 

the  mixture  is  liable  to  rise  sufficiently  high  to  cause  the  formation 
of  light-colored  meta-hydroxide.  But  the  liquids  must  not  be  ice- 
cold. 

The  official  solution  of  ferric  sulphate,  containing  27.8  per  cent 
of  Fe2(SO4)3,  yields  14.84  pei:  cent  of  ferric  hydroxide.  The 
official  solution  of  ferric  chloride,  containing  38.7  per  cent  of 
FeQ3,  yields  about  24.92  per  cent  of  Fe(OH)3. 

Should  the  quantity  of  ammonia  used  be  insufficient,  or  should 
it  be  added  to  the  ferric  sulphate  instead  of  vice  versa,  basic  ferric 
salts  will  be  formed.  If  the  H3N  is  added  to  the  iron  solution  a 
dark  red-brown  solution  containing  ferric  salt  is  obtained  at  first, 
and  no  ferric  hydroxide  is  thrown  down  until  more  ammonia  is 
added. 

Ferric  hydroxide  may  also  be  precipitated  from  ferric  chloride 
or  ferric  nitrate,  and  soda  may  be  used  as  a  precipitant  instead  of 
ammonia. 

If  solution  of  ferric  chloride  is  used  the  hydroxide  formed  is 
more  easily  washed  free  from  the  ammonium  salts.  If  ferric  ni- 
trate is  used,  the  product  is  soluble  in  an  excess  of  potassium  car- 
bonate (Stahl's  tincture). 

Ferric  hydroxide  precipitated  with  soda  instead  of  ammonia  is 
lighter  in  color  and  extremely  difficult  to  wash  free  from  sodium 
salt. 

Ferric  hydroxide  forms  very  soluble  compounds,  with  sugar 
and  with  glycerin.  It  is  also  soluble  in  solutions  of  ferric  salts, 
as  in  solution  of  ferric  chloride.  The  precipitation  of  ferric  hy- 
droxide from  solutions  of  ferric  salts  by  means  of  alkalies  is 
prevented  by  the  presence  of  citric  acid,  tartaric  acid,  sugar,  gly- 
cerin, and  certain  other  organic  substances. 

Description. — When  moist  it  is  a  dark  red-brown  magma,  in- 
soluble in  water,  but  soluble  in  citric,  tartaric,  acetic,  hydrochloric, 
sulphuric,  and  nitric  acids.  When  dried  it  is  a  reddish-brown 
amorphous  powder,  less  readily  soluble  in  acids  than  the  moist 
hydroxide. 

Uses.  For  the  preparation  of  ferric  acetate,  citrate,  tartrate, 
nitrate,  etc.  Also  as  an  antidote  for  arsenic,  with  which  it  forms 
insoluble  arsenate : 

4Fe(OH)8+As20,=Fe.,(As04)2+Fe(OH)2+5H20. 


IRON  HYDROXIDE.  413 

For  whatever  purpose  it  may  be  required  it  must  be  freshly  pre- 
pared, as  it  cannot  be  preserved  from  decomposition  by  which 
meta-hydroxides  are  formed,  which  in  no  case  can  take  the  place 
of  the  freshly  precipitated  ferric  hydroxide. 

Iron  (Ferric)  Hydroxide  with  Magnesia. 

FERRI      HYDROXIDUM    CUM    MAGNESIA. 

[Antidote  for  Arsenic.] 

Solution  of  normal  ferric  sulphate  (65  Gm, 

or)    50  ml 

Magnesia    10  Gm 

Mix  the  solution  of  tersulphate  of  iron  with  130  ml  of  water. 

Stir  the  magnesia  with  about  150  ml  of  water  to  a  thin  milky 
mixture,  transfer  this  at  once  to  a  wide-mouthed  bottle  of  two 
liters'  capacity,  and  add  one  liter  of  water. 

If  the  magnesium  oxide  mixed  with  15  times  its  weight  of  water 
be  allowed  to  stand  too  long  before  the  remainder  of  the  water  is 
added  it  will  form  a  firm  gelatinous  mass  of  magnesium  hydrox- 
ide. 

The  two  liquids  should  be  kept  in  a  cool  place,  and  as  these 
materials  are  intended  exclusively  for  the  preparation  of  an  effec- 
tive antidote  for  arsenical  poisoning,  the  particular  place  where 
they  are  to  be  found  must  be  well  known  by  every  one  concerned. 

When  the  antidote  is  wanted,  the  solution  of  ferric  sulphate  is 
at  once  poured  into  the  magnesia  milk,  and  the  mixture  thoroughly 
shaken.  It  is  then  ready  for  immediate  use. 

The  preparation  contains  ferric  hydroxide,  magnesium  hydrox- 
ide and  magnesium  sulphate. 

Another  Formula. 

"Antidote  for  arsenic"  is  prepared  as  follows,  according  to  the 
Pharmacopceia  of  the  Netherlands: 

Ferric"  chloride  90  Gm 

Distilled  water  550  ml 

Make  a  solution,  and  keep  it  in  a  bottle. 


414  IRON    HYPOPHOSPHITE. 

Magnesia    28  Gm 

Distilled  water  520  Gm 

Mix  well  and  keep  this  mixture  in  another  bottle. 
When  required  for  use  mix  equal  volumes  of  the  two  liquids 
and  shake  well. 


IRON  (FERRIC)  HYPOPHOSPHITE. 

FERRI    HYPOPHOSPHIS. 

Fe(P02H2)8=25i. 

L,  tj  L|J^  Sulphate  of  iron  and  ammonium 30  parts 

Sodium  hypophosphite   20  parts 

Dissolve  each  salt  in  150  parts  of  water,  and  filter  the  solutions. 
Add  the  solution  of  the  iron 'alum  to  that  of  the  sodium  hypophos- 
phite, stirring  constantly.  Set  aside  for  a  few  hours.  Transfer 
the  precipitate  to  a  wetted  filter  or  muslin  strainer,  drain  it  thor- 
oughly, and  wash  it  with  150  parts  of  cold  distilled  water.  Drain, 
press  out  as  much  as  possible  of  the  moisture  from  the  magma, 
and  dry  the  product  between  blotting  paper  with  the  aid  of  gentle 
heat,  protecting  the  preparation  as  far  as  practicable  from  the  air. 

Reaction.     2  ( FeH4N  ( SO4 )  2. 1 2H2O)  +6  ( NaPO2H2  .H2O) 

=  2Fe(P02H2)3+(H4N)2S04+3Na2S04+3oH20. 

s 

Notes.  The  quantity  of  water  used  is  necessarily  limited  to 
prevent  loss,  because  ferric  hypophosphite  is  not  quite  insoluble 
in  water,  and  if  the  washing  should  be  done  with  the  large  quan- 
tities of  water  required  to  thoroughly  remove  the  sulphates  of  the 
mother  liquor  from  the  bulky  magma  of  hypophosphite,  consider- 
able loss  must  follow,  if  not  the  disappearance  of  the  entire 
product.  The  precipitate  must,  therefore,  be  carefully  freed  from 
all  mother  liquor  that  can  be  removed  by  draining  it  before  it  is 
•washed,  and  the  quantity  of  water  prescribed  for  washing  it 
should  not  be  exceeded. 

Ferric  hypophosphite  is  soluble  in  a  strong,  hot  solution  of 
citrates  of  potassium  and  sodium. 

Description. — A  grayish  powder,  odorless  and  almost  tasteless, 


IRON  IODIDE.  415 

slightly  soluble  in  water,  readily  soluble  in  acetic  acid,  and  in 
solutions  of  potassium  citrate  or  of  sodium  citrate. 


IRON    (FERROUS)  IODIDE. 

FERRI      IODIDUM. 

FeI2=3o9. 

Iron  wire,  cut   6  parts 

Iodine    17  parts 

Distilled  water 20  parts 

Digest  in  a  flask  at  a  moderate  heat  until  all  odor  of  iodine  has 
ceased  and  a  green  solution  has  been  obtained.  Filter  the  solu- 
tion and  evaporate  the  filtrate  as  rapidly  as  possible  in  a  polished 
iron  dish  until  a  trial  drop  solidifies  on  cooling.  Then  pour  the 
liquid  out  on  a  porcelain  slab,  and  as  soon  as  it  has  hardened  break 
it  into  pieces  while  still  warm,  and  put  it  into  small,  dry,  warm 
bottles,  which  must  be  at  once  tightly  stoppered. 

For  reaction  and  notes  see  Syrup  of  Ferrous  Iodide. 

Description. — Ferrous  iodide  is  a  crystalline  solid,  which,  in 
^mass,  appears  nearly  black.    In  solution  it  is  green.    But  the  prod- 
uct easily  decomposes,  and  it  is  for  that  reason  scarcely  employed 
except  in  the  form  of  "saccharated  iodide  of  iron,"  or  as  "syrup 
of  ferrous  iodide." 

Saccharated  Ferrous  Iodide. 

FERRI     IODIDUM     SACCHARATUM. 

Iron,  in  the  form  of  fine,  bright  wire,  cut 

into  small  pieces   6  parts 

Reduced  iron I  part 

.Iodine    17  parts 

Distilled  water. 

Dry  milk  sugar,  of  each,  sufficient. 

Mix  the  iron  wire,  iodine  and  20  parts  of  distilled  water  in  a 
flask,  and  shake  them  together  occasionally  until  the  reaction 
ceases,  and  the  liquid  has  acquired  a  green  color  and  lost  the  odor 
of  iodine.  Warm  the  flask  and  contents,  if  necessary,  to  com- 
plete the  reaction.  Filter  the  liquid  through  a  small  white  paper 


IRON  IODIDE. 

filter  previously  wetted  with  distilled  water,  into  a  porcelain  dish 
containing  about  40  parts  of  powdered  milk  sugar.  Rinse  the 
flask  and  the  undissolved  iron  wire  with  a  little  distilled  water, 
and  pass  the  rinsings  through  the  same  filter  as  before  used  into 
the  porcelain  dish. 

Mix  the  contents  of  the  dish  by  stirring  with  a  glass  rod  or 
porcelain  spatula.  Evaporate  the  water  from  the  mixture  by 
water-bath  heat,  stirring  frequently,  until  a  dry  mass  remains. 
Transfer  the  dry  residue  while  still  hot  to  a  clean,  bright  iron 
mortar  heated  by  placing  it  in  boiling  water  and  then  wiped  dry, 
powder  it,  add  the  reduced  iron  and  enough  powdered  milk  sugar 
to  make  the  weight  of  the  total  product  100  parts,  and  triturate 
these  ingredients  together  until  intimately  mixed  and  reduced  to  a 
fine  powder. 

Transfer  the  powder  at  once  to  small,  warm,  perfectly  dry  bot- 
tles, which  should  be  filled,  and  tightly  stoppered. 

Notes.  See  the  reaction  and  remarks  given  under  the  title  of 
Syrup  of  Ferrous  Iodide. 

The  ferrous  iodide  contained  in  this  preparation  is  protected 
from  decomposition  by  the  milk  sugar  and  the  reduced  iron.  It 
should  -contain  at  least  20  per  cent  of  ferrous  iodide. 

Description. — A  yellowish-white,  grayish-white,  or  greenish- 
gray  powder ;  odorless ;  hygroscopic ;  having  a  sweetish,  ferrugi- 
nous taste.  Soluble  in  7  parts  of  water  at  15°. 

Syrup  of  Ferrous  Iodide. 

SYRUPUS     FERRI    IODIDI. 

A  syrupy  liquid  containing  10  per  cent  of  ferrous  iodide  (FeI2, 
309). 

Iron,  in  the  form  of  fine  wire,  and  cut  into 

small  pieces 25  Gm 

Iodine    83  Gm 

Sugar,  in  coarse  powder 600  Gm 

Distilled  water,  sufficient. 

Introduce  the  iron  into  a  flask,  add  200  ml  of  distilled  water, 
and  afterward  the  iodine.  Shake  the  mixture  occasionally,  until 
the  reaction  ceases  and  the  solution  has  acquired  a  green  color  and 


IRON  IODIDE.  417 

has  lost  the  odor  of  iodine.  Place  the  sugar  in  a  porcelain  dish 
and  filter  the  solution  of  ferrous  iodide  into  the  sugar.  Rinse  the 
flask  and  iron  wire  with  90  ml  of  distilled  water,  and  pass  the 
washings  through  the  filter  into  the  sugar.  Stir  the  mixture  with 
a  glass  rod,  heat  it  to  the  boiling  point  on  a  sand-bath,  and  having 
filtered  the  syrup  through  white  paper  into  a  tared  bottle,  add 
enough  distilled  water  to  make  the  product  weigh  1000  Gm  . 
Lastly,  shake  the  bottle,  which  should  be  completely  filled  and 
securely  stoppered. 

Reaction.    2Fe+2l2=2FeI,. 

Notes.  The  proportion  of  iron  combining  with  8.20  parts  of 
iodine  to  form  ferrous  iodide  is  only  a  little  over  1.80  parts,  so  that 
the  iron  is  present  in  large  excess.  This  is  to  facilitate  the  com- 
plete saturation  of  the  iodine.  At  first  the  reaction  is  tardy,  and 
may  require  the  aid  of  heat  to  start  it ;  but  as  soon  as  some  ferrous 
iodide  has  been  formed  the  iodine  dissolves  in  the  solution,  and 
after  that  the  liquid  acts  rapidly  on  the  iron  with  the  evolution  of 
heat.  If  this  elevation  of  temperature  is  too  great  there  will  be  a 
loss  of  iodine  by  vaporization.  The  heat  must  not  be  so  great  that 
violet  vapors  appear  in  the  flask.  It  is  safest  to  add  the  iodine  in 
small  portions  at  a  time,  during  brisk  stirring,  waiting  for  the 
liquid  to  become  green  instead  of  red-brown  after  each  addition 
before  adding  more. 

The  reaction  between  iron  and  iodine  will  take  place  at  all  tem- 
teratures,  but  is  slow  in  cold.  Should  the  reaction  proceed  at  a 
comparatively  low  temperature  until  all  the  iodine  has  been  added, 
and  cease  without  leaving  a  liquid,  of  bright  green  color  when 
filtered,  the  application  of  heat  before  removing  the  undissolved 
iron  will  always  bring  out  the  green  color,  which,  together  with 
the  absence  of  iodine  odor,  is  the  sign  of  completed  reaction. 

To  prevent  oxidization  the  solution  of  ferrous  iodide  should  be 
filtered  as  rapidly  as  possible  and  while  still  hot,  directly  into  the 
sugar. 

Success  in  preparing  a  perfect  syrup  of  iodide  of  iron  depends 
upon  a  perfectly  completed  reaction,  careful  control  of  the  tem- 
perature so  that  no  iodine  shall  be  lost,  the  use  of  pure  distilled 
water  and  pure  white  sugar,  and  scrupulous  cleanliness  in  regard 
to  the  vessels  and  implements  used. 

Syrup  of  iodide  of  iron  may  be  successfully  preserved  in  corked 

Vol.    11—27 


4l8  IRON  IODIDE. 

bottles,  but  with  much  less  risk  in  glass-stoppered  bottles.  Ex- 
posure to  light  seems  to  decolorize  the  preparation,  even  after  the 
green  color  has  changed  to  a  pale  yellowish.  But  in  order  to  best 
preserve  a  bright  green  syrup  of  ferrous  iodide  from  change  it 
should  be  kept  in  a  shaded  place. 

Long  exposure  to  light  almost  completely  decolorizes  the  prep- 
aration, and  the  sugar  in  the  syrup  becomes  to  a  great  extent  in- 
verted (J.  H.  Long). 

Unless  the  bottle  containing  the  syrup  is  rilled,  the  surface  of 
the  preparation  soon  becomes  yellow  or  yellowish-brown  from 
oxidation  by  contact  with  the  air  above  it.  Hence  the  direction 
that  the  bottle  shall  be  rilled. 

When  this  preparation  becomes  slightly  discolored — yellowish- 
green  but  not  yellow  or  yellowish-brown— the  bright  green  color 
can  usually  be  restored  by  heating  it  to  near  the  boiling  point  in  a 
flask  by  means  of  a  water-bath. 

Straining  does  not  suffice  to  make  the  product  clear.  It  must 
be  filtered  through  white  filter-paper. 

As  the  preparation  is  prone  to  discoloration  by  decomposition, 
assuming  a  yellowish-brown  color  from  free  iodine,  various  means 
have  been  suggested  to  prevent  this  change.  It  was  at  one  time 
proposed  to  place  a  piece  of  polished  iron — for  example,  a  nail 
filed  until  bright  over  its  whole  surface — in  the  syrup ;  but  this  is 
worse  than  useless.  Another  and  more  successful  plan  was  to 
add  tartaric  or  citnc  acid,  in  the  proportion  of  about  i  part  in  500. 
All  such  additions  are,  however,  unnecessary,  as  the  preparation 
will  keep  well  if  properly  made  and  put  into  clean,  glass-stop- 
pered bottles  in  the  manner  indicated  above. 

Description. — Must  be  perfectly  clear  pale  green,  odorless,  with 
a  sweet  strongly  ferruginous  taste.  Reaction  neutral.  Sp.  w. 
about  1.353  at  15°. 

The  size  of  the  container  should  be  determined  by  the  rate  at 
which  the  preparation  is  dispensed  in  the  pharmacy.  It  should 
not  be  so  large  that  the  contents  may  not  be  entirely  consumed 
in  a  few  weeks.  Bottles  holding  500  Gm  are  as  large  as  should 
be  used,  and  bottles  containing  100  Gm  are  not  too  small  when 
the  demand  for  the  preparation  is  limited. 

The  same  preparation  (containing  10  per  cent  of  ferrous  iodide) 
is  contained  in  all-  other  pharmacopoeias. 


IRON    LACTATE.  419 

Glycerite  of  Ferrous  Iodide. 

Iodine   83  Gm 

Iron  wire 25  Gm 

Distilled  water 150  ml 

Glycerin   , 300  ml 

Digest  the  iron  wire  and  iodine  together  in  the  water,  con- 
tained in  a  flask,  until  the  liquid  has  acquired  a  bright  green 
color,  and  lost  all  odor  of  iodine.  Filter  the  solution  into  the 
glycerin,  mix  well,  and  evaporate  the  mixture  until  it  weighs 
500  Gm. 

Notes.  This  glycerite  keeps  indefinitely,  mixes  clear  with 
water,  alcohol,  and  syrup,  and  is  exactly  twice  the  strength  (in 
ferrous  iodide)  of  the  Pharmacopceial  syrup  of  iodide  of  iron 
(U.  S.). 

IRON  (FERROUS)  LACTATE. 

FERRI    LACTAS. 

Fe(C3H503)2.3H20=288. 

Whey looo  ml 

Milk   sugar 50  Gm 

Sodium  bicarbonate 60  Gm 

Ferrous   sulphate 40  Gm 

The  white  of  two  eggs. 
Diluted  sulphuric  acid. 
Water. 

Add  the  milk  sugar  to  one  liter  of  the  clear  whey  obtained  from 
spontaneously  soured  skimmed  milk,  in  a  cylindrical  vessel  of 
about  two  cubic  decimeters  capacity.  Let  the  mixture  stand  in 
a  place  where  the  temperature  is  maintained  at  between  30°  and 
45°.  After  fermentation  has  commenced  (within  a  day  or  two) 
and  the  liquid  is  sour  from  lactic  acid,  neutralize  with  a  portion 
of  the  sodium  bicarbonate.  Repeat  this  neutralization  every  day 
or  two,  adding  each  time  enough  sodium  bicarbonate  to  com- 
pletely neutralize  the  lactic  acid  formed. 

When  the  mixture  no  longer  acquires  a  decidedly  acid  reaction 
within  three  or  four  days  after  neutralization,  and  when  about 
60  Gm  of  sodium  carbonate  has  been  consumed,  add  enough  di- 


42O  IRON    LACTATE. 

luted  sulphuric  acid  to  render  the  liquid  distinctly  acid.  Then 
add  the  whites  of  two  eggs.  Mix  thoroughly. 

Now  heat  the  mixture  to  boiling.  Filter  the  hot  liquid. 
Evaporate  the  filtrate  to  about  250  ml. 

Dissolve  the  ferrous  sulphate  in  80  ml  of  hot  distilled  water, 
and  filter.  Add  this  solution  while  hot  to  the  hot  solution  of  so- 
dium lactate.  Remove  from  the  hot  mixture  the  brown  flocculent 
precipitate  formed,  passing  the  liquid  through  a  flannel  strainer. 
Set  the  hot  colature  aside  in  a  cold  place  for  two  days.  Collect 
the  crystallized  ferrous  lactate  on  a  strainer.  Let  the  crystalline 
mass  be  well  drained.  Wash  it  with  a  little  cold  distilled  water, 
and  afterwards  with  a  little  alcohol.  Press  the  moist  lactate  be- 
tween blotting  paper,  changing  the  paper  several  times.  Dry  the 
product  well  with  the  aid  of  moderate  heat. 

Keep  the  product  in  small  tightly  closed  bottles  in  a  cool,  dry 
place. 

Reactions. 

C12H2Ai+H20=4HC8HB08;  then 

HC3H5O3+NaHCO3= NaC3H5O3+H2O+CO2 ;    and,    finally, 

2NaC3H503+FeS04=Fe(C3H503)2+Na2S04. 

Notes.  The  whey  contains  4  to  5  per  cent  of  milk-sugar,  and 
this,  together  with  that  added,  yields  lactic  acid,  as  shown  above. 

Unless  this  acid  is  neutralized  from  time  to  time,  the  lactic 
fermentation,  which  ordinarily  continues  for  a  week,  may  change 
to  vinous  and  acetic  fermentation.  The  production  of  alcohol  and 
acetic  acid  might  also  follow  if  the  temperature  of  the  liquid  is 
below  20°  C. 

C12H22011+H20^4C2H5OH+4C02. 

Should  the  temperature  be  allowed  to  exceed  40°  C.,  or  an  in- 
sufficient quantity  of  milk-sugar  be  used,  butyric  acid  will  be 
formed. 

2HC3H5O3=HC4HTO2+3CO2+2H2. 

To  arrest  further  fermentation,  the  liquid  is  heated  to  the  boil- 
ing point,  which  at  the  same  time  coagulates,  and  facilitates  the 


IRON   LACTATE.  421 

removal  of  albuminoid  matters.  Dilute  sulphuric  acid  is  added  to 
prevent  the  formation  of  ferric  salt,  throwing  down  ferric  hydrate, 
which  is  filtered  out,  and  to  neutralize  any  alkali  which  may  have 
been  added  in  excess. 

The  crystals  of  ferrous  lactate  are  removed  from  the  mother 
liquor,  and  then  rinsed  free  from  sodium  sulphate  by  cold  water, 
after  which  the  water  adhering  to  the  salt  is  washed  off  with  a 
little  alcohol  to  facilitate  subsequent  drying.  The  product  must 
be  dried  at  not  above  30°  to  40°  as  rapidly  as  practicable  to  pre- 
vent oxidation. 

If  not  thoroughly  dry  when  put  up  it  soon  oxidizes. 

A  preparation  entirely  free  from  ferric  lactate  cannot  be  pro- 
duced. The  less  ferric  salt  the  preparation  contains,  the  greener 
will  be  its  color.  It  should  have  the  proper  greenish  color,  and 
yield  a  greenish  solution  with  water.  As  the  solution  of  this  salt 
in  water  is  always  a  slow  process,  the  ferrous  lactate  should  be 
triturated  to  fine  powder  before  adding  the  water. 

Another  Method. 

Crystallized  calcium  lactate '. 500  Gm 

Hydrochloric  acid 320  ml 

Iron  wire 100  Gm 

Distilled  water,  sufficient. 

Put  the  iron  into  a  mixture  of  the  acid  with  200  ml  of  water 
contained  in  a  flask.  When  effervescence  has  ceased,  heat  to 
the  boiling  point.  Let  cool.  Filter  the  solution.  Add  enough 
water  to  make  the  solution  measure  600  ml. 

Dissolve  the  crystallized  calcium  lactate  in  2  liters  of  boiling 
distilled  water. 

Mix  the  solutions  and  set  the  mixture  aside  in  a  cool  place  for 
two  or  three  days. 

Collect  the  ferrous  lactate  on  a  filter,  wash  it  with  a  little 
alcohol,  and  dry  it  at  a  temperature  not  exceeding  50°  C. 

Reaction.     FeCl2+Ca(C3HrA)2= Fe(C3HrA)2+CaCl2. 

Notes.  An  additional  amount  of  ferrous  lactate  may  be  recov- 
ered from  the  mother  liquor  by  adding  alcohol  to  it  and  allowing 
it  to  stand  a  few  hours,  ferrous  lactate  being  almost  insoluble  in 
alcohol  while  calcium  chloride  is  soluble  in  it. 


422  IRON   OLEATE. 

Description. — Yellowish  green  crystalline  masses,  or  a  greenish 
white  powder,  nearly  inodorous,  having  a  sweetish  ferruginous 
taste,  and  a  slightly  acid  reaction.  Soluble  in  40  parts  of  water 
at  15°  C,  and  in  12  parts  of  boiling  water.  Freely  soluble  with 
a  green  color  in  solutions  of  alkali  citrates.  Nearly  insoluble  in 
alcohol. 

IRON  (FERRIC)  OLEATE. 

FERRI    OLEAS. 

Fe(C18H3302)  3=899. 

Solution  of  normal  ferric  sulphate 90  ml 

White  castile  soap,  in  fine  powder 1 50  Gm 

Dilute  the  solution  of  ferric  sulphate  with  5,000  ml  of  water, 
and  dissolve  the  soap  in  2,500  ml  of  hot  water.  Mix  the  solutions. 
Wash  the  precipitated  oleate  twice  with  hot  water,  using  about 
ten  liters  each  time. 

Reaction. 

Fe2  ( S04)  3+6NaC18H3302=2Fe  ( C18H33O2 )  3+3Na2SO4. 

Notes.     The  yield  is  about  120  Gm. 

Ferrous  oleate  can  also  be  made  by  'double  decomposition,  from 
ferrous  sulphate  and  soap,  but  the  greenish  ferrous  oleate  soon 
oxidizes. 

Description. — Ferric  oleate  is  a  dark  red  plaster-like  solid. 
Soluble  in  oleic  acid  and  in  fixed  oils. 

IRON  (FERROUS)  OXALATE. 

FERRI    OXALAS. 

FeC2O4.H2O=i62. 

Ferrous  sulphate 330  Gm 

Oxalic  acid 1 50  Gm 

Ammonia  water 300  ml 

Dissolve  the  oxalic  acid  in  the  ammonia  water  diluted  with 
2,000  ml  of  water;  and  the  ferrous  sulphate  in  3,000  ml  of  hot 


IRON  OXALATE.  423 

water ;  filter  the  solutions,  and  then  mix  them.  Wash  the  pre- 
cipitate by  decantation  and  afterwards  on  a  filter  until  the  wash- 
ings are  tasteless.  Dry  the  product  between  bibulous  paper,  with 
the  aid  of  gentle  heat. 

Reaction. 

FeS04+(H4N)2C204=FeC204+(H4N)2S04. 

Notes.  Ferrous  oxalate  can  also  be  made  by  the  process  official 
in  the  U.  S.  P.  of  1870,  which  prescribed  ferrous  sulphate  dis- 
solved in  water  to  be  added  to  a  solution  of  oxalic  acid.  When 
this  process  is  followed  ferrous  oxalate  and  free  sulphuric  acid 
are  formed,  the  precipitate  separates  slowly,  and  a  considerable 
loss  results  from  the  fact  that  the  oxalate  is  not  insoluble  in  the 
sulphuric  acid.  By  neutralizing  nearly  all  of  the  oxalic  acid  with 
ammonia,  using  a  slight  excess  of  oxalic  acid,  and  mixing  the 
solution  of  ferrous  sulphate  with  the  acid  solution  of  ammonium 
oxalate,  the  precipitate  falls  at  once,  and  no  loss  of  product  is 
sustained.  If  a  perfectly  neutral  solution  of  ammonium  oxalate 
is  used,  the  product  will  have  a  dull  reddish  yellow  color. 

To  obtain  a  bright  yellow  ferrous  oxalate  the  mother  liquor  in 
which  the  precipitate  is  formed  must  be  decidedly  acid. 

Description. — A  light-yellow  crystalline  powder ;  odorless ; 
nearly  tasteless.  Nearly  insoluble  in  water,  and  insoluble  in  alco- 
hol. 

IRON  (FERRIC)  OXIDE. 

FERRI    OXIDUM. 

Fe2O3=i6o. 

Heat  dried  ferric  hydroxide  strongly  until  it  ceases  to  lose 
weight. 

2Fe(OH)3=Fe203+3H20. 

Seven  parts  of  dry  ferric  hydroxide  will  yield  rather  more  than 
five  parts  of  oxide.  It  is  brown-red. 

Another  Method. 
Heat  ferrous  oxalate  until  completely  decomposed. 


424  IRON  OXIDE. 

4FeC2O4+3O2=2Fe2O3+8CO2. 

The  product  obtained  from  ferrous  oxalate  is  extremely. finely 
divided  and  therefore  soft  and  of  a  rich,  dark-brown  color.  This 
is  used  by  jewellers  to  polish  gold. 

Magnetic  Oxide  of  Iron. 
Fe304=232. 

Solution  of  ferric  sulphate,  U.  S 230  ml 

Ferrous   sulphate 60  Gm 

Ammonia  water  ( 10%  of  H3N) 500  ml 

Water. 

Dissolve  the  ferrous  sulphate  in  two  liters  of  water  and  filter. 
Add  the  solution  of  ferric  sulphate. 

Dilute  the  ammonia  water  with  one  liter  of  water. 

Pour  the  iron  solution  gradually  into  the  diluted  ammonia 
water,  stirring  well. 

Set  the  mixture  aside  to  settle.  Decant  the  supernatant  liquid 
from  the  precipitate.  Then  add  enough  water  to  make  the  whole 
mixture  measure  about  three  liters. 

Boil  this  mixture  about  fifteen  minutes,  or  until  the  brown 
ferroso-ferric  hydroxide  is  changed  to  the  nearly  black  ferroso- 
ferric  oxide. 

Wash  the  precipitate,  first  by  affusion  and  decantation  of  hot 
water,  and  afterwards  on  a  filter,  until  the  washings  cease  to  give 
a  precipitate  with  test-solution  of  barium  chloride.  Then  dry  the 
product  with  the  aid  of  heat. 

Reaction. 

Fe2  ( SO4 )  8+FeSO4+8H4NOH 

=Fe20,.FeO+4(H4N)2S04+4H20. 

Description. — A  fine,  heavy,  brownish-black,  odorless  and  taste- 
less powder. 


IRON  OXIDE.  425 

Another  Method. 

Ferrous    sulphate 300  parts 

Sulphuric   acid 39  parts 

Nkric   acid 28  parts 

Ammonia  water 640  parts 

Distilled  water,  sufficient. 

Add  the  sulphuric  acid  slowly  to  200  parts  of  distilled  water 
in  a  porcelain  dish,  stirring  constantly.  Heat  the  mixture  to  a 
temperature  of  over  90°  C.  on  a  water-bath.  Add  the  nitric  acid 
and  mix  well.  Then  add  the  ferrous  sulphate  gradually,  stirring 
constantly,  waiting  after  each  addition  until  effervescence  ceases 
before  adding  more.  When  two-thirds  of  the  ferrous  sulphate 
has  been  added,  the  remaining  100  Gm  of  that  salt  may  be  added 
at  once,  together  with  500  parts  of  distilled  water.  When  the 
salt  has  completely  dissolved,  filter  the  solution ;  then  add  10,000 
parts  of  distilled  water. 

Mix  the  ammonia  water  with  3,000  parts  of  distilled  water. 

Pour  the  iron  solution  slowly  into  the  dilute  ammonia  solution, 
stirring  constantly. 

When  the  precipitate  has  subsided,  decant  the  supernatant 
liquid,  transfer  the  ferroso-ferric  hydroxide  to  a  porcelain  dish, 
add  an  equal  volume  of  water,  and  boil  the  mixture  about  fifteen 
minutes  or  until  the  color  of  the  precipitate  is  changed  from  brown 
to  black.  Wash  the  ferroso-ferric  oxide  with  boiling  water  unti! 
the  washings  are  no  longer  affected  by  barium  nitrate  test  solu- 
tion. Let  the  oxide  drain,  press  out  from  it  as  much  of  the  water 
as  it  is  practicable  to  remove  by  that  means,  and  dry  the  product 
as  rapidly  as  practicable. 

When  perfectly  dry,  keep  it  in  well-stoppered  bottles. 

IRON    PHOSPHATE;    BLUE. 

FERRI    PHOSPHAS    COERULEUS. 

[•Ferroso-ferric  Phosphate.     Composition  perhaps 

Fe,(P04),.FeP04.i2H20.] 

Ferrous    sulphate 30  parts 

Sodium   phosphate 28  parts 

Sodium   acetate 10  parts 


426  IRON  PHOSPHATE. 

Dissolve  the  ferrous  sulphate  and  the  sodium  phosphate  each 
in  300  parts  of  boiling  water,  filter,  and  allow  the  solutions  to  cool 
to  about  40°  to  50°  C.  (104°  to  122°  F.).  Dissolve  the  sodium 
acetate  in  50  parts  of  warm  water.  Add  the  solution  of  ferrous  sul- 
phate to  the  solution  of  sodium  phosphate,  and  lastly  add  the  solu- 
tion of  sodium  acetate.  Mix  well.  As  soon  as  the  precipi- 
tate has  subsided,  decant  the  mother  liquor.  Wash  the  precipitate, 
either  by  decantation  or  on  a  muslin  strainer,  with  hot  water, 
until  the  washings  cease  to  give  a  precipitate  with  solution  of 
barium  chloride.  Dry  the  product  at  not  over  50°  C.  (122°  F.). 

Reaction. 

3FeS04.+2Na2PH04=Fe3  ( PO4 )  2+2Na2SO4+  H2SO4. 

The  sulphuric  acid  then  reacts  with  the  sodium  acetate,  form- 
ing free  acetic  acid,  in  which  the  phosphate  of  iron  is  but 
sparingly  soluble,  and  the  precipitated  ferrous  phosphate  is  par- 
tially oxidized. 

Notes.  Unless  sodium  bicarbonate,  sodium  acetate,  or  sodium 
phosphate  in  excess  be  added,  a  portion  of  the  ferroso-ferric  phos- 
phate remains  in  solution  in  the  free  acid  formed  by  the  reaction, 
and  loss  ensues.  By  neutralizing  the  free  sulphuric  acid  with 
sodium  bicarbonate,  which  does  not  affect  the  precipitate  already 
formed,  all  of  the  phosphate  of  iron  is  thrown  down.  When  first 
formed  the  precipitate  is  grayish-white  or  bluish-gray ;  it  soon 
becomes  grayish-blue,  and  should  retain  this  color  until  washed 
and  dried.  The  color  may  be  easily  spoiled,  however,  by  too  high 
heat,  or  by  too  long  exposure  to  the  action  of  the  mother  liquor, 
or  to  the  air  during  the  process  of  washing  and  drying.  Instead 
of  bluish  the  color  may  become  greenish-gray.  The  surest  way 
to  obtain  a  handsome  grayish-blue  product  is  to  employ  sodium 
acetate,  as  directed  in  the  foregoing  formula.  After  drying,  the 
product  must  be  powdered  and  sifted.  Dried  at  a  high  heat,  the 
preparation  forms  very  hard  lumps ;  but  if  dried  by  moderate  heat 
it  may  be  easily  rubbed  through  a  fine  sieve  without  using  much 
force. 

This  product  is  the  Ferri  Phosphas  of  the  British  Pharmaco- 
poeia and  of  the  U.  S.  P.  of  1870. 

It  should  contain  at  least  47  per  cent  of  ferrous  phosphate.  It 
may  also  contain  some  ferric  oxide. 


IRON  PHOSPHATE.  .  427 

Description. — A  fine,  grayish-blue,  odorless,  tasteless,  insoluble 
powder. 

IRON    PHOSPHATE    SYRUP. 

SYRUPUS    FERRI    PHOSPHATIS. 

Precipitated  ferrous  sulphate .     28  Gm 

Sodium  phosphate   25  Gm 

Sodium  bicarbonate 7  Gm 

Phosphoric  acid  (50%) 136  Gm 

Sugar    : 450  Gm 

Dissolve  the  ferrous  sulphate  in  about  300  ml  of  boiling  water, 
and  the  sodium  phosphate  in  a  similar  quantity  of  cold  water ; 
mix  the  solutions ;  add  the  sodium  carbonate  previously  dissolved 
in  100  ml  of  water,  and,  after  stirring  well,  transfer  the  precipitate 
to  a  muslin  filter  and  wash  it  with  distilled  water  until  the  filtrate 
ceases  to  be  affected  by  test  solution  of  barium  chloride.  Mix  the 
washed  and  drained  precipitate  in  a  mortar  with  the  phosphoric 
acid.  As  soon  as  the  phosphate  is  dissolved,  filter  the  solution  into 
a  bottle,  add  400  ml  of  distilled  water  and  the  sugar,  and  shake 
until  dissolved,  without  the  aid  of  heat.  Lastly,  add  sufficient 
distilled  water  to  make  the  final  product  measure  660  ml. 

Notes.  The  product  contains  about  I  Gm  of  anhydrous  phos- 
phate of  iron  (Fe3(PO4)2)  in  one  imperial  fluidrachm.  If  the 
quantity  obtained  by  the  above  formula  be  diluted  with  30  ml  of 
simple  syrup,  the  preparation  will  then  contain  i  Gm  to  each  4  ml. 

Another  Method. 

Iron  wire,  polished,  cut. 7  Gm 

Phosphoric  acid  (50%) 120  Gm 

Distilled  water  40  ml 

Simple  syrup 600  ml 

Put  the  iron  wire,  acid,  and  water  into  a  flask,  being  careful  that 
the  metal  is  completely  covered  by  the  liquid ;  insert  a  loose  plug 
of  cotton  in  the  neck  of  the  flask,  and  set  it  aside  for  two  or  three 
days.  When  the  iron  is  dissolved,  filter  the  liquid,  add  the  syrup, 
and  lastly  enough  distilled  water  to  make  the  final  product  meas- 
ure 820  ml. 


428  IRON  PHOSPHATE. 

Note.     This  preparation  is  identical  with  that  of  the  British 
Pharmacopoeia. 

Description. — A  clear,  nearly  colorless,  thick  syrup  of  acid  and 
ferruginous  taste. 


IRON   (FERRIC)   PHOSPHATE;  PRECIPITATED. 

FERRI     PHOSPHAS     PRAECIPITATUS. 

FePO4.2H2O=i87. 

Solution  of  normal  ferric  sulphate 660  ml 

Sodium  phosphate   450  Gm 

Sodium  acetate 170  Gm 

Dilute  the  solution  of  ferric  sulphate  with  4000  ml  of  water; 
add  the  sodium  acetate,  and  dissolve.  Dissolve  the  sodium  phos- 
phate in  4000  ml  of  water,  and  filter,  if  necessary.  Pour  the  solu- 
tion of  ferric  sulphate  and  sodium  acetate  gradually  into  that  of 
the  sodium  phosphate,  stirring  well.  Wash  the  precipitate  with 
warm  water  until  the  washings  are  free  from  sulphate.  Collect 
and  dry  the  precipitate  with  the  aid  of  gentle  heat. 

Reaction.    Fe2  ( SO4)  3+2  ( Na2HPO4. 1 2H.O )  + 

2(NaC2H3O2.3H2O)+4H2O=2FePO4.2H2O 

+3(Na2S04.ioH20)+2HC2H302. 

Notes.  It  will  be  seen  from  the  equation  that  the  sodium  ace- 
tate is  added  simply  to  prevent  the  formation  of  free  sulphuric 
acid,  which  would  occasion  loss  of  ferric  phosphate,  which  is 
soluble  in  that  acid  but  insoluble  in  acetic  acid. 

The  precipitate  is  white  or  cream-colored  and  very  voluminous. 
On  this  account  it  is  difficult  to  wash.  When  the  quantity  oper- 
ated upon  admits  of  it,  the  washing  should  be  effected  by  mixing 
the  precipitate  with  warm  water  in  a  tall  vessel,  allowing  it  to 
settle,  drawing  off  the  clear  supernatant  liquid  by  means  of  a 
siphon,  and  then  transferring  the  magma  to  a  wetted  muslin 
strainer,  where  it  may  be  left  to  drain  thoroughly.  This  operation 
is  to  be  repeated  if  necessary. 


IRON  PHOSPHATE.  429 

When  the  precipitate  is  allowed  to  remain  long  in  contact  with 
the  mother  liquor  it  gradually  becomes  more  dense ;  also  when  the 
washing  is  too  long  continued.  If  large  quantities  are  operated 
upon  the  washing  consumes  several  days. 

Description. — A  white,  or  cream-colored,  odorless,  tasteless,  in- 
soluble powder.  Soluble  in  dilute  orthophosphoric  acid,  but 
insoluble  in  dilute  metaphosphoric  acid  (difference  from  the  pyro- 
phosphate). 

Iron  (Ferric}  Phosphate;  Soluble. 

FERRI    PHOSPHAS    SOLUBILIS. 

Ferric  citrate   10  parts 

Sodium  phosphate 1 1  parts 

Distilled  water 20  parts 

Dissolve  the  ferric  citrate  in  the  water  with  the  aid  of  water- 
bath  heat.  Add  the  sodium  phosphate  to  the  solution,  and  stir 
constantly  until  it  shall  have  been  dissolved.  Evaporate  the  solu- 
tion over  the  water-bath,  at  a  temperature  not  exceeding  60°  C, 
to  the  consistence  of  thick  syrup,  spread  it  on  glass  plates,  and  let 
it  dry  to  form  scales. 

The  product  should  be  kept  in  dark  amber-colored  bottles, 
tightly  closed. 

Notes.  The  solution  of  the  ferric  citrate  in  water  is  brownish- 
red  ;  this  color  is  not  immediately  changed  on  the  addition  of  the 
sodium  phosphate,  but  when  the  reaction  has  taken  place  by  which 
ferric  phosphate  and  sodium  citrate  are  formed  the  solution  turns 
green.  The  sodium  phosphate  used  must  not  be  to  any  degree  ef- 
floresced. 

Description. — Thin,  green,  clear,  transparent  scales,  odorless,  of 
an  acidulous,  slightly  saline  taste.  Permanent  in  dry  air  when 
excluded  from  light.  Becomes  darkened  and  brownish  on  ex- 
posure to  light.  It  is  readily,  freely  and  perfectly  soluble  in  water, 
but  insoluble  in  alcohol.  The  water-solution  has  a  slightly  acid 
reaction. 


43O  IRON  PHOSPHATE. 

Syrup  of  the  Phosphates  of  Iron,  Quinine,  and  Strychnine. 

Soluble  ferric  phosphate   20  Gm 

Quinine   sulphate    30  Gm 

Strychnine    0.2  Gm 

Phosphoric  acid    48  ml 

Glycerin    100  ml 

Water 50  ml 

Syrup. 

Heat  the  soluble  ferric  phosphate  with  the  water,  in  a  porcelain 
capsule,  until  it  is  dissolved.  Then  add  the  phosphoric  acid,  the 
quinine  sulphate,  and  the  strychnine,  and  stir,  until  solution  is  ef- 
fected. Filter  the  liquid  into  the  glycerin,  contained  in  a  grad- 
uated bottle,  add  enough  syrup  to  make  up  the  volume  to  one  liter 
and  mix  thoroughly.  Lastly,  strain,  if  necessary. 

Description. — A  clear,  pale-green  syrup;  odorless;  of  bitter, 
acid  taste.  The  preparation  shows  a  bluish  fluorescence. 

Ammonio- Ferric  Citro-Phosphate. 
[Soluble  Phosphate  of  Iron  with  Citrate  of  Ammonium.] 

Add  the  washed  precipitated  ferric  phosphate  obtained  by  the 
formula  given  on  p.  —  from  66  ml  of  solution  of  normal  ferric 
sulphate  and  45  Gm  of  sodium  phosphate,  to  60  ml  of  di-ammon- 
ium  hydrogen  citrate  prepared  by  the  formula  given  under  the 
head  of  Ammonium  Citrate.  Heat  the  mixture  by  means  of  a 
water-bath  for  three  hours,  stirring  occasionally,  taking  care  not 
to  allow  the  temperature  to  exceed  60°  C.  Evaporate  the  solution 
to  the  consistence  of  syrup,  spread  it  on  plates  of  glass,  and  dry 
it  in  scales. 

Notes.  The  ferric  phosphate  is  added  in  slight  excess  in  order 
to  perfectly  saturate  the  solution  with  it. 

If  60  ml  of  solution  of  di-sodium-hydrogen  citrate  be  used  in- 
stead of  the  citrate  of  ammonium,  the  product  will  be  the  Pharma- 
copoeial  soluble  "phosphate  of  iron.'' 


IRON   PYROPHOSPHATE.  43! 

IRON   (FERRIC)    PYROPHOSPHATE;  PRECIPITATED. 

FERRI     PYROPHOSPHAS      PRAECIPITATUS. 

Fe4(P207)  3= 


Solution  of  normal  ferric  sulphate  ......   500  ml 

Sodium  pyrophosphate   ................   320  Gm 

Dilute  the  solution  of  ferric  sulphate  with  3500  ml  of  water,  and 
dissolve  the  pyrophosphate  of  sodium  in  4000  ml  of  hot  water. 
Filter  the  liquids.  Pour  the  solution  of  ferric  sulphate  slowly  into 
that  of  the  pyrophosphate,  stirring  well.  Wash  the  precipitate 
with  warm  water  on  a  wetted  muslin  strainer  until  the  washings 
are  free  from  sulphate.  Dry  the  product  by  the  aid  of  gentle 
heat. 

Reaction.     2Fe2  (  SO4)  3+3Na4P2O7=Fe4  (  P2O7)  3+6Na2SO4. 

Notes.  The  solutions  must  be  cold  when  mixed,  and  the  iron 
solution  must  be  added  very  slowly  to  that  of  the  sodium  salt,  with 
constant  and  brisk  stirring.  The  precipitate  is  very  light  and 
bulky,  and  hence  quite  difficult  to  wash. 

Description.  —  A  white  or  cream-colored,  odorless  and  tasteless 
powder.  Insoluble  in  water.  Soluble  in  dilute  metaphosphoric 
acid  but  insoluble  in  dilute  orthophosphoric  acid.  [Difference  from 
the  phosphate  (orthophosphate).] 

Iron  (Ferric)  Pyrophosphate;  Soluble. 

FERRI    PYROPHOSPHAS    SOLUBILIS. 

[  Sodio-Ferric  Citro-Py  rophosphate.  ] 

Ferric  citrate   .........................   5  parts 

Sodium  pyrophosphate  .................   5  parts 

Dissolve  the  citrate  in  10  parts  of  distilled  water  heated  on  a 
water-bath,  add  the  pyrophosphate,  and  continue  the  heating  with 
constant  stirring  until  the  pyrophosphate  of  sodium  is  dissolved 
and  the  solution  turns  green.  Evaporate  at  a  temperature  not 
exceeding  60°  C.  (140°  F.)  until  the  solution  has  the  consistence 
of  thick  syrup  ;  spread  it  on  glass  plates,  and  dry  it  in  scales. 


432  IRON   PYROPHOSPHATE. 

Notes.  Sodium  citrate  has  been  substituted  for  ammonium 
citrate  for  the  preparation  of  pyrophosphate  of  iron  by  the  Phar- 
macopoeia, on  the  ground  that  the  ammonio-ferric  salt  became 
insoluble  through  loss  of  ammonia,  and  because  it  either  darkened 
or  became  opaque  by  age.  The  sodio-ferric  pyrophosphate,  ho'w- 
ever,  is  also  liable  to  become  impaired  by  age  and  exposure  to 
light.  The  preparation  is  difficult  to  scale  satisfactorily.  In  small 
quantities  it  may  be  best  scaled  in  the  cold.  Pyrophosphate  of 
iron  should  be  carefully  protected  against  light.  It  is  best  pre- 
served.in  amber-colored  bottles,  tightly  corked,  and  kept  in  a  dry, 
cool,  dark  place. 

Soluble  ferric  pyrophosphate  with  ammonium  citrate  may  be 
prepared  by  adding  the  precipitated  ferric  pyrophosphate  obtained 
from  500  ml  of  solution  of  normal  ferric  sulphate  and  320  Gm  of 
sodium  pyrophosphate  to  460  ml  of  the  solution  of  di-ammonium 
hydrogen  citrate  and  digesting  at  not  over  60°  C.  for  three  hours, 
or  until  no  more  of  the  ferric  pyrophosphate  dissolves.  The  solu- 
tion is  then  filtered,  evaporated,  and  the  preparation  scaled. 

Description. — Thin,  transparent,  green  scales ;  odorless ;  taste  a 
little  acidulous,  slightly  saline.  Freely  soluble  in  water.  Insol- 
uble in  alcohol. 

Another  Method. 
[After  the  Swiss  Pharmacopoeia.] 

Sodium  pyrophosphate 75  parts 

Solution  of  ferric  chloride,  U.  S.  P 97  parts 

Citric  acid    26  parts 

Ammonia  water, 

Distilled  water,  of  each  sufficient. 

Dissolve  the  sodium  pyrophosphate  in  500  parts  of  distilled 
water. 

Dilute  the  solution  of  ferric  chloride  with  800  parts  of  distilled 
water. 

Pour  the  iron  solution  a  little  at  a  time  into  the  solution  of 
sodium  pyrophosphate,  stirring  uninterruptedly. 

Wash  the  precipitate  thoroughly  in  the  usual  way. 

Dissolve  the  citric  acid  in  50  parts  of  distilled  water  with 
enough  ammonia  water  to  render  the  solution  slightly  alkaline.. 


IRON   SACC KARATE.  433 

Add  the  moist,  precipitated  ferric  pyrophosphate  to  the  solution 
of  ammonium  citrate,  stir  well,  and  heat  at  not  over  50°  C.  until 
solution  is  effected. 

Filter  the  solution,  evaporate  it,  and  scale  the  product  in  the 
usual  way. 

Solution  of  Sodio-Ferric  Pyrophosphate. 
[Solution  Leras.] 

Ferric   chloride    6  parts 

Sodium  pyrophosphate 17  parts 

Distilled  water,  sufficient. 

Dissolve  the  ferric  chloride  in  500  parts  of  distilled  water. 
Dissolve  the  sodium  pyrophosphate  in  500  parts  of  distilled 
water. 

Mix  the  solutions.     Filter. 

Description. — A  pale  yellowish,  clear  liquid  of  alkaline  reaction. 
Gently  heated  with  an  equal  volume  of  acetic  acid  it  yields  a  white 
gelatinous  precipitate  which  is  blackened  by  hydrogen  sulphide. 

It  contains  about  0.114  to  0.119  per  cent  of  Fe. 

IRON  SACCHARATE,  OR  SOLUBLE  SACCHARATED 

IRON. 

FERRI     SACCHARATUM     SOLUBILE. 

[Saccharated  Oxide  of  Iron.     Iron  Sugar.] 

Solution  of  ferric  chloride  (U.  S.  P.)..   230  parts 

Sodium  carbonate   260  parts 

'Solution  of  sodium  hydroxide  (15%)..      50  parts 
Sugar,  pure,  granulated, 
Distilled  water,  each,  sufficient. 

Dilute  the  solution  of  ferric  chloride  with  1500  parts  of  dis- 
tilled water. 

Dissolve  the  sodium  carbonate  in  1500  parts  of  distilled  water. 

Pour  the  solution  of  sodium  carbonate,  a  little  at  a  time,  into  the 
diluted  solution  of  ferric  chloride,  during  uninterrupted  stirring, 
taking  care,  until  toward  the  close,  to  wait  after  each  addition  of 
the  sodium  carbonate  solution  until  the  precipitate  formed  shall 

Vol.  11—28 


434  IRON  SACCHARATE. 

have  redissolved  before  adding  the  next  portion  of  the  alkali  car- 
bonate. 

When  finally  all  of  the  sodium  carbonate  solution  has  been 
added,  the  precipitate  is  to  be  washed  by  the  affusion  and  decan- 
tation  of  distilled  water  until  the  washings,  when  diluted  with  5 
volumes  of  water,  no  longer  give  any  precipitate  with  silver  nitrate 
test-solution  but  only  rendered  opalescent  by  it. 

Transfer  the  magma  to  a  cloth  strainer  and  let  it  drain.  Ex- 
press as  much  of  the  water  from  the  drained  magma  as  practicable 
by  moderate  pressure. 

Put  the  still  wet  solid  mass  into  a  porcelain  dish  and  add  500 
parts  of  sugar,  together  with  the  solution  of  sodium  hydroxide 
and  mix  well. 

Heat  the  mixture  over  a  water-bath  until  a  clear  solution  is 
formed. 

Evaporate  the  liquid,  by  the  water-bath  heat,  during  constant 
stirring,  to  dryness,  and  powder  the  residue. 

Add  enough  sugar  to  make  the  total  weight  of  the  product  1000 
parts  and  reduce  it  to  a  medium  fine  powder. 

Notes.    The  product  is  a  water-soluble  ferric  sodio-saccharate. 

145  parts  of  crystalline  ferric  chloride  may  be  used  instead  of 
230  parts  of  the  official  (U.  S.  P.)  solution. 

When  the  sodium  carbonate  solution  is  added  to  the  solution  of 
ferric  chloride  effervescence  takes  place  from  the  CO2  liberated 
and  the  precipitate  at  first  formed,  consisting  of  ferric  hydroxide, 
redissolves  in  the  solution  of  ferric  chloride.  But  when  more  than 
one-half  of  the  sodium  carbonate  solution  has  been  added  and 
much  sodium  chloride  is  accordingly  contained  in  the  liquid,  the 
precipitate  formed  afterwards  redissolves  no  longer. 

Description. — A  red-brown  powder  having  a  sweet  and  slightly 
ferruginous  taste.  One  part  of  it  dissolved  in  20  parts  of  boiling 
water  forms  a  perfectly  clear  red-brown  solution  having  a  feebly 
alkaline  reaction.  It  contains  from  2.8  to  3  per  cent  of  Fe. 

Another  Method. 

Solution  of  ferric  chloride 230  parts 

Distilled  water,  cold   170  parts 

Sugar,  granulated  100  parts 

Make  a  solution. 


IRON    SUBCARBONATE.  435 

Add  to  this  solution,  gradually  and  with  constant  stirring,  400 
parts  of  solution  of  sodium  hydroxide  of  15  per  cent  strength. 

Let  the  mixture  stand  a  few  hours  (until  it  becomes  clear). 

Then  add  5000  parts  of  boiling  water. 

The  precipitate  which  is  now  formed  is  then  washed  by  the  af- 
fusion and  decantation  of  distilled  water  until  the  washings  have 
but  a  feebly  alkaline  reaction  and  begin  to  be  colored. 

Transfer  the  well-drained  precipitate  to  a  porcelain  dish  and 
add  900  parts  of  powdered  sugar,  mix  well,  and  dry  the  mixture 
over  a  water-bath,  stirring  constantly.  Add  enough  powdered 
sugar  to  the  dry  residue  to  make  the  total  weight  of  the  product 
1000  parts. 

Notes.  It  is  recommended  that  the  diluted  ferric  chloride  solu- 
tion and  the  sodium  hydroxide  solution  shall  both  be  cold  when 
mixed.  The  boiling  water  afterwards  added  makes  the  precipitate 
denser  and  easier  to  wash.  When  about  one-half  of  the  alkali 
solution  has  been  added  a  precipitate  is  formed,  but  this  gradually 
redissolves  as  the  remainder  of  the  alkali  is  added  and  the  liquid 
becomes  clear  on  standing  a  few  hours.  The  boiling  water  is  then 
added. 

Saccharated  iron  should  make  a  clear  solution  in  5  parts  of 
distilled  water. 

"Sirupus  Ferri  Oxydati" 

of  the  German  Pharmacopoeia  is  a  syrup  made  out  of  equal  parts 
of  saccharated  iron,  distilled  water,  and  simple  syrup.  It  contains 
or  represents  I  per  cent  of  its  weight  of  Fe. 

IRON    SUBCARBONATE. 

FERRI     SUBCARBONAS. 

Ferrous  sulphate  8  parts 

Sodium  carbonate 9  parts 

Dissolve  the  salts,  each  in  40  parts  of  boiling  water,  filter,  and 
pour  the  solution  of  iron  sulphate  into  that  of  the  sodium  car- 
bonate, with  constant  stirring.  Wash  the  precipitate  with  cold 
water,  first  by  decantation  and  afterwards  on  a  muslin  strainer, 
until  the  washings  cease  to  be  precipitated  by  test  solution  of 


436  IRON   SUBCARBONATE. 

barium  chloride.     Then  drain,  and  dry  tl.e.  precipitate  without 
heat. 

Reaction.  FeSO4+Na2CO8=FeCO8+Na2SO4.  The  ferrous 
carbonate  oxidizes,  as  explained  in  the  note. 

Notes.  To  insure  that  the  sodium  carbonate  is  in  excess  over  the 
ferrous  sulphate,  which  is  necessary  to  insure  complete  double  de- 
composition, add  the  solution  of  the  iron  salt  to  the  solution  of 
sodium  carbonate.  The  solutions  should  be  hot  in  order  that  the 
ferrous  carbonate  formed  may  be  heavy,  and  also  to  prevent  the 
formation  of  soluble  bicarbonate.  When  cold  solutions  are  used 
a  portion  of  the  precipitate,  which  is  at  first  nearly  white,  soon 
decomposes,  losing  a  portion  of  its  carbonic  acid,  which  combines 
with  another  portion  of  ferrous  carbonate  and  holds  it  in  solution 
as  bicarbonate.  After  a  time  this,  too,  decomposes,  the  carbonic 
acid  being  liberated  and  ferric  hydroxide  is  formed  by  the  ab- 
sorption of  oxygen  from  the  air.  When  hot  solutions  are  used  the 
carbonic  acid  is  rapidly  expelled  and  the  perfect  precipitation  of 
the  iron  compound  not  retarded.  Owing  to  gradual  oxidation  the 
precipitate  rapidly  changes  color  in  contact  with  the  air,,  passing 
through  various  shades  of  gray,  green,  blue,  olive,  brown,  and 
red.  The  gray,  green,  blue  and  olive  are  due  to  ferroso-ferric  hy- 
droxide, while  the  brown  and  red  are  caused  by  ferric  hydroxide. 
Finally,  the  precipitate  becomes  almost  completely  ferric.  Dried 
at  high  heat  the  preparation  is  more  red,  and  less  readily  soluble 
in  hydrochloric  acid. 

The  ferric  hydroxide  generally  rises  to  the  surface  of  the  mixed 
liquids,  and  during  the  washing  of  the  precipitate  the  surface  of 
the  magma  becomes  covered  with  it,  while  the  interior  continues 
bluish-gray  or  green.  The  washing  is  best  effected  with  boiling 
water,  and  on  a  muslin  filter.  The  pores  of  the  filter-paper  be- 
come rapidly  closed  by  yellowish-red  ferric  hydroxide. 

Dried  at  ordinary  temperatures  the  preparation  is  olive-brown 
with  a  reddish  tint,  retaining  a  small  amount  of  ferrous  carbonate, 
and  is  easily  powdered.  Dried  with  the  aid  of  considerable  heat 
the  product  is  brown-red,  and  cakes  together  in  hard  lumps,  which 
are  not  so  readily  powdered. 

Description. — A  red  or  brown-red,  odorless,  tasteless,  insoluble 
powder. 


IRON  SULPHATE.  437 

IRON  (FERROUS)   SULPHATE. 

FERRI     SULPHAS. 

FeH2S05.6H20=278. 

Iron  in  the  form  of  clean,  bright  wire,  cut 

small    3  parts 

Sulphuric  acid 5  parts 

Water,  sufficient. 

Put  15  parts  of  water  in  a  flask  or  dish  and  add  the  sulphuric 
acid  very  gradually,  stirring  constantly.  Then  add  the  iron. 
When  effervescence  has  nearly  ceased,  heat  the  contents  to  boiling 
for  about  ten  minutes.  Filter  while  hot.  Set  aside  to  crystallize. 

Collect  the  crystals  and  dry  them  on  filter  paper. 

Evaporate  the  mother  liquor  to  one-half  its  weight,  again  set 
aside  to  crystallize,  and  collect  the  second  crop  of  crystals  in  the 
manner  as  the  first. 

Reaction.    Fe+H2SO4+7H2O=FeH2SO5.6H2O-fH2. 

Notes.  The  iron  is  used  in  excess  of  amount  required  by  theory 
in  order  that  no  ferric  salt  may  be  formed.  The  hydrogen,  which 
is  liberated  in  the  chemical  reaction,  has  a  disagreeable  odor  from 
volatile  carbon,  sulphur,  and  phosphorus  compounds. 

To  prevent  contamination  with  ferric  salt,  the  filtrate  may 
be  acidulated  with  sulphuric  acid  before  being  set  aside  to 
cool ;  any  ferric  sulphate  present  will  remain  in  the  mother  liquor. 

The  crystals  should  be  dried  as  rapidly  as  practicable  to  avoid 
oxidation,  which  easily  takes  place  when  the  salt  is  moist.  To 
facilitate  the  drying  the  crystals  may  be  hastily  washed  with  a  little 
alcohol,  which  evaporates  rapidly. 

Re  crystallized  Ferrous  Sulphate. 

Green  vitriol    10  parts 

Water    15  parts 

Diluted  sulphuric  acid   i  part 

Make  a  solution  with  the  aid  of  heat.  Boil  it  until  a  filtered 
sample  is  of  a  bluish-green  color.  Then  filter  while  hot.  and  set 
the  solution  aside  to  crystallize  in  the  usual  way.  Drain  and  dry 


438  IRON   SULPHATE. 

the  crystals  as  rapidly  as  possible  and  at  once  bottle  the  product 
in  a  dry  container  to  be  tightly  closed. 

Notes.  The  crystals  must  have  a  bluish-green  and  not  a  yellow- 
ish-green color,  and  they  must  be  perfectly  clear.  The  ferric  sul- 
phate and  other  ferric  compounds  contained  in  the  green  vitriol 
are  removed  partly  by  the  boiling  and  nitration,  and  partly  in  the 
crystallization  when  the  ferric  sulphate  present  remains  in  the 
mother  liquor. 

Granulated  Ferrous  Sulphatz. 

Ferrous  sulphate 100  Gm 

Boiling  distilled  water 100  ml 

Diluted  sulphuric  acid 5  ml 

Alcohol    25  ml 

Dissolve  the  ferrous  sulphate  in  the  water,  add  the  acid,  and 
filter  the  solution  while  hot.  Evaporate  at  once  in  a  tared  porce- 
lain dish  over  a  sand-bath  until  the  weight  of  the  liquid  is  reduced 
to  150  Gm  .  Then  cool  it  quickly,  stirring  uninterruptedly. 

Transfer  the  liquid  and  crystals  to  a  glass  funnel  loosely  stopped 
with  absorbent  cotton,  and,  when  the  liquid  has  passed  off,  pour 
the  alcohol  over  the  mass  of  crystals  in  the  funnel.  When  the 
alcohol  has  passed  through,  transfer  the  crystals  to  bibulous 
paper  and  dry  them  quickly  at  the  ordinary  temperature  and 
transfer  the  dry  product  at  once  to  well-stoppered  bottles. 

Precipitated  Ferrous  Sulphate. 

Iron  wire   2  parts 

Sulphuric  acid  3  parts 

Distilled  water 12  parts 

Alcohol    6  par 

Add  the  sulphuric  acid  gradually  to  the  water,  stirring  well. 
Add  the  iron  to  the  warm  mixture.  When  effervescence  has 
nearly  ceased  heat  the  mixture  at  the  boiling  point  for  about  ten 
minutes.  Filter  while  hot.  Add  a  small  quantity  of  sulphuric 
acid  to  the  filtrate.  Then  pour  the  solution  into  the  alcohol,  stir- 
ring constantly. 

Collect  the  precipitated  crystalline  ferrous  sulphate  on  a  filter, 
transfer  it  to  bibulous  paper,  and  dry  it  quickly  at  the  ordinary 


IRON   SULPHATE.  439 

room  temperature,  stirring  the  crystals  often  and  changing  the 
paper  once  or  twice  to  facilitate  rapid  drying. 

When  thoroughly  dry,  put  the  product  in  dry  bottles  to  be  well 
corked  or  stoppered. 

Notes.  Iron  is  used  in  excess  and  the  acid  is  saturated  with  it. 
Free  sulphuric  acid  is  added  to  the  solution  because  the  salt  crys- 
tallizes best  from  an  acid  solution. 

Ferrous  sulphate  is  insoluble  in  alcohol,  but  ferric  sulphate  is 
soluble.  Hence  any  ferric  sulphate  present  will  remain  in  the 
alcoholic  liquid. 

The  crystals  wet  with  alcohol  instead  of  water  dry  rapidly  and 
are  moreover  surrounded  by  an  atmosphere  of  alcohol  vapor  in- 
stead of  air,  so  that  the  process  of  drying  is  accomplished  with  far 
less  danger  of  oxidation. 

Turbidated  FerroiCs  Sulphate. 

Ferrous  sulphate  100  parts 

Distilled  water 100  parts 

Diluted  sulphuric  acid 5  parts 

Alcohol    25  parts 

Dissolve  the  ferrous  sulphate  in  the  water,  heated  to  the  boiling 
point,  add  the  acid,  and  filter  the  hot  solution.  Evaporate  the 
filtrate  in  a  tared  porcelain  dish  over  a  sand-bath  until  the  weight 
of  the  contents  is  reduced  to  150  parts  and  then  cool  it  quickly, 
stirring  constantly.  Transfer  the  wet  salt  mass  to  a  glass  funnel 
the  throat  of  which  is  loosely  closed  with  a  plug  of  absorbent  cot- 
ton, and  when  the  product  has  well  drained  pour  the  alcohol  upon 
it.  When  the  alcohol  has  passed  through  it  spread  the  crystalline 
salt  upon  bibulous  paper,  dry  it  quickly  at  the  ordinary  tempera- 
ture, and  transfer  it  at  once  to  perfectly  dry  bottles  and  close  these 
tightly. 

The  product  is  a  pale  bluish-green  crystalline  powder.  Its  offi- 
cial title  (U.  S.  P.,  1890)  is  "Granulated  Ferrous  Sulphate." 

Description. — Ferrous  sulphate  forms  large,  clear,  transparent, 
bluish-green  crystals,  or  a  crystalline  granular  salt ;  odorless  ;  taste 
saline,  styptic,  ferruginous.  Efflorescent  in  dry  air.  On  exposure 
it  becomes  first  whitish  on  the  surface,  then  yellowish,  brownish  or 
reddish  from  ferric  compounds.  Soluble  in  1.8  parts  of  water  at 
15°,  and  in  0.3  part  of  boiling  water.  Insoluble  in  alcohol. 


44O  IRON   SULPHATE. 

IRON  (FERROUS)  SULPHATE.    DRIED. 

FERRI    SULPHAS    EXSICCATUS. 

Approximately  FeH2SO5=i7o. 

Crystallized  ferrous  monometa-sulphate  contains  6  molecules 
of  water.  When  moderately  heated  it  dissolves  in  its  water  of 
crystallization ;  between  33°  C.  and  90°  C.  the  salt  loses  that  water. 
At  280°  C.  partial  decomposition  of  the  sulphate  is  liable  to  take 
place. 

In  exsiccating  ferrous  sulphate,  liquefaction  of  the  salt,  by 
solution  in  its  water  of  crystallization,  must  be  avoided  if  a  light- 
colored  product,  unoxidized  and  free  from  hard  particles,  is  to  be 
obtained.  The  ferrous  sulphate  should  be  pure,  and  granulated, 
precipitated,  or  reduced  to  coarse  powder.  It  may  then  be  spread 
out  in  a  thin  layer  on  paper  and  be  placed  in  a  drying  room  where 
the  temperature  is  about  40°  C.  The  drying  may  also  be  effected 
by  the  heat  of  the  sun  until  thoroughly  effloresced,  or  converted 
into  a  white  powder.  Occasional  stirring  is  required.  Should 
the  temperature  exceed  50°  C.  the  salt  partly  dissolves  in  its  water 
of  crystallization  and  the  liquid  penetrates  the  paper.  Delf  plates 
may  be  used  instead  of  paper,  or  porcelain  or  iron  dishes. 

If  the  salt  is  allowed  to  become  so  hot  as  to  dissolve  in  its  water 
of  crystallization,  it  will  oxidize  more  rapidly,  and  becomes  dis- 
colored. After  having  effloresced,  however,  it  will  no  longer 
liquefy  even  at  water-bath  heat,  or  higher  temperatures. 

If  water-bath  heat  is  used  in  finishing  the  exsiccation,  several 
days'  heating  will  be  necessary  to  expel  the  last  portions  of  the 
sixth  molecule  of  water ;  but  an  almost  white  product  may  readily 
be  obtained,  amounting  to  about  64  to  65  per  cent  of  the  crystal- 
lized salt,  without  prolonging  the  heating  over  water-bath 
beyond  a  few  hours,  the  powder  being  well  stirred  during  the 
process. 

To  get  rid  of  the  remainder  of  the  water  it  is  necessary  to  raise 
the  heat  to  about  120°  to  150°  C.,  continuing  the  heat  until  the 
product  ceases  to  lose  weight.  This  prolonged  exposure  inevi- 
tably results  in  a  dark-colored  product. 

To  avoid  decomposition  and  discoloration  the  Pharmacopoeia 
no  longer  requires  the  product  to  be  absolute  FeH.,SO5,  but  allows 
some  moisture  in  it. 


IRON   SULPHATE.  441 

It  should  be  triturated  to  fine  powder  and  sifted. 
Dried  ferrous  sulphate  must  be  put  in  dry  bottles. 
One  Gm  of  dried  ferrous  sulphate  corresponds  to  about  ij  Gm 
of  the  crystallized  salt. 

Description. — A  fine,  grayish  (almost  white)  powder,  slowly 
but  completely  soluble  in  water. 

Iron    (Ferrous)   Ammonium  Sulphate. 

Ferrous  sulphate  100  parts 

Ammonia  water 123  parts 

Diluted  sulphuric  acid 360  parts 

Add  the  diluted  sulphuric  acid  gradually  to  the  ammonia  water, 
stirring  well.  Dissolve  the  ferrous  sulphate  in  the  mixture.  Fil- 
ter, if  necessary.  Evaporate  the  solution  to  crystallization. 

Description. — The  product  is  not  a  double  salt  but  a  mixture  of 
an  equal  number  of  molecules  of  ferrous  sulphate  and  ammonium 
sulphate.  It  is  pale-green,  readily  water-soluble. 


IRON    SUBSULPHATE. 

FERRI     SUBSULPHAS. 

(Basic  Ferric  Sulphate.    Monsel's  Pozvder.) 

When  solution  of  basic  ferric  sulphate  is  evaporated  at  a  mod- 
erate heat  upon  a  delf  or  glass  plate,  the  residue  consists  of  trans- 
parent scales,  which  deliquesce  on  exposure.  When  dried  at  a 
higher  temperature,  the  salt  turns  yellow  and  becomes  less  hygro- 
scopic. When  the  solution  is  painted  upon  an  iron  plate  with  a 
brush,  and  the  plate  heated  over  a  naked  flame,  the  residue  is  a 
porous  crust,  which  should  be  at  once  removed,  and  powdered 
while  still  hot  in  a  warm  mortar.  The  product  thus  obtained  is 
yellow,  quite  hygroscopic,  and  perfectly  uniform. 

If  the  solution  is  evaporated  to  dryness  in  a  dish,  stirring  the 
drying  mass,  and  continuing  the  heat  until  a  dry  powder  is  formed, 
the  product  is  a  coarse,  grayish-yellow,  gritty  powder,  not  as 
readily  soluble  in  water. 

Monsel's  powder  should  be  a  fine,  yellow,  hygroscopic  powder. 
It  must  be  kept  in  a  tightly  corked  bottle. 


442  IRONt  SUBSULPHATE. 

Solution  of  Basic  Ferric  Sulphate. 
(Monsel's  Solution.) 

An  aqueous  solution  containing  about  43.5  per  cent  of 
basic  ferric  sulphate  of  varying  chemical  composition,  con- 
sisting perhaps  principally  of  a  compound  represented  by  the 
formula  Fe4O(SO4)  5=720.  The  proportion  of  iron  compound 
in  the  solution  corresponds  to  about  13.6  per  cent  of  metallic  iron. 
It  is  prepared  as  follows : 

Ferrous  sulphate 135  parts 

Sulphuric  acid,  92.5%   14  parts 

Nitric  acid,  68%. 

Distilled  water,  each,  sufficient. 

Add  the  sulphuric  acid  gradually  to  100  parts  of  distilled  water 
in  a  roomy  porcelain  dish,  pouring  the  acid  slowly  and  in  a  thin 
stream  into  the  water,  stirring  constantly  with  a  glass  rod.  Heat 
the  mixture  to  a  temperature  of  nearly  100°  C. ;  add  15  parts  of 
nitric  acid  and  mix  well. 

Divide  the  coarsely  powdered  ferrous  sulphate  into  four  equal 
portions,  and  add  these  portions,  one  at  a  time,  to  the  hot  liquid, 
waiting  after  each  addition  until  effervescence  has  nearly  ceased. 

When  all  the  ferrous  sulphate  has  been  added,  and  has  dis- 
solved, add  a  few  drops  of  nitric  acid,  and,  if  this  causes  a  further 
evolution  of  red  fumes  continue  to  add  more  nitric  acid,  a  few 
drops  at  a  time,  until  it  no  longer  causes  nitrous  vapors  to  be 
evolved. 

Then  boil  the  solution  until  it  assumes  a  ruby-red  color  and  is 
free  from  nitrous  odor. 

Lastly  add  enough  distilled  water  to  make  the  total  product 
weigh  200  parts. 

Filter  if  necessary. 

Keep  the  product  in  glass-stoppered  bottles  in  a  moderately 
warm  place  (not  below  22°  C.),  protected  from  light. 

Reaction. 
i2FeH2SO5.6H2O+3H2S04+4HNO3 

=3(Fe40(S04)5)  +  i2H20+4NO. 
Notes.     See  the  notes  under  the  title  of  Solution  of  Ferric 


IRON    TERSULPHATE. 


443 


Sulphate.  Note  that  the  only  difference  between  the  formulas 
for  the  preparation  of  solution  of  normal  ferric  sulphate  and  the 
solution  of  basic  ferric  sulphate,  respectively,  is  that  about  twice 
as  much  sulphuric  acid  is  employed  in  proportion  to  the  ferrous 
sulphate  to  make  the  normal  ferric  sulphate  as  is  prescribed  for 
making  the  subsulphate. 

The  quantity  of  nitric  acid  prescribed  is  a  little  scant. 

Solution  of  basic  ferric  sulphate  sometimes  crystallizes  and 
forms  a  semi-solid  whitish  mass,  if  kept  in  a  room  too  cold. 
Should  this  happen,  the  mass  may  be  easily  liquefied  again  by 
warming  it.  If  kept  in  a  sufficiently  warm  place,  as  directed,  it 
does  not  crystallize. 

This  solution  is  also  called  "solution  of  subsulphate  of  iron." 

Description. — A  clear  dark  red-brown  liquid;  almost  odorless; 
taste  strongly  styptic,  acid.  Sp.  w.  about  1.550  at  15°. 

On  slowly  mixing  2  volumes  of  the  solution  with  i  volume  of 
concentrated  sulphuric  acid,  in  a  beaker,  a  semi-solid  white  mass 
will  separate  on  standing  (difference  from  ter sulphate). 


IRON  (FERRIC)  SULPHATE    SOLUTION. 

LIQUOR    FERRI    TERSULPHATIS. 

(Solution  of  Tersulphate  of  Iron.) 

An  aqueous  solution  of  normal  ferric  sulphate 

[Fe2(S04)  3=400] 

containing  about  28.7  per  cent  of  that  salt,  corresponding  to 
about  8  per  cent  of  metallic  iron. 

Ferrous  sulphate 400  Gm 

Sulphuric  acid    (92.5%) 77  Gm 

Nitric  acid   (68$>). 

Distilled  water,  each,  sufficient. 

Add  the  sulphuric  acid  gradually  and  with  constant  stirring  to 
200  milliliters  of  distilled  water  in  a  capacious  porcelain  dish ; 
heat  the  mixture  to  100°  C. ;  then  add  44  Gm  of  nitric  acid,  and 
mix  well. 

Divide  the  ferrous  sulphate,  coarsely  powdered,  into  four  equal 
portions,  and  add  these  portions,  one  at  a  time,  to  the  hot  liquid, 


444  IRON    TERSULPHATE. 

waiting  after  each  addition  until  effervescence  has  nearly  ceased. 

When  all  the  ferrous  sulphate  has  been  added  and  has  dissolved, 
add  a  few  drops  of  nitric  acid,  and,  if  this  causes  a  further  evolu- 
tion of  red  fumes,  continue  to  add  more  nitric  acid,  a  few  drops 
at  a  time,  until  it  no  longer  causes  red  fumes  to  be  evolved. 

Then  boil  the  solution  until  it  assumes  a  reddish-brown  color 
and  is  free  from  nitrous  odor. 

Lastly,  add  enough  distilled  water  to  make  the  whole  product 
weigh  1,000  Gm.  Filter,  if  necessary. 

Reaction.     6FeH2SO5.6H2O+3H2SO4+2HNO3 

=3Fe2(S04)3-HiH20+2NO. 

Notes.  The  ferrous  sulphate  used  must  be  in  clear  crystals  and 
dry ;  or,  in  other  words,  it  must  be  dry  but  not  in  any  degree 
effloresced.  If  granulated,  precipitated  or  turbidated  ferrous  sul- 
phate is  used  it  need  not  be  powdered  at  all. 

The  oxidation  of  ferrous  sulphate  to  ferric  sulphate  by  nitric 
acid  takes  place  much  below  100°  C.  (212°  F.).  Water-bath 
heat  is,  therefore,  sufficient  for  this  purpose.  The  process  is, 
however,  hastened  by  the  application  of  a  somewhat  higher  de- 
gree of  heat. 

To  oxidize  all  the  ferrous  salt  is  not  difficult,  a  sufficient  amount 
of  nitric  acid  being  used.  But  the  preparation  must  be  free  from 
nitric  acid  when  finished,  and  it  is  difficult  to  expel  the  excess 
which  is  almost  always  added  in  order  to  complete  the  oxidation. 
Hence,  great  care  shou1  *  be  taken  not  to  use  more  nitric  acid  than 
is  necessary. 

But  the  presence  of  a  trace  of  nitric  acid  is  less  objectionable 
in  this  preparation  than  the  presence  of  ferrous  salt. 

When  the  ferrous  salt  is  being  raised  to  ferric  by  means  of 
the  nitric  and  sulphuric  acids,  a  very  dark-brown  or  almost  black 
compound  is  formed  by  the  ferric  salt  with  the  nitrogen  oxide. 
Hence  the  liquid  grows  nearly  black  at  times  and  the  evolution 
of  nitrous  vapors  is  at  the  same  time  temporarily  arrested.  But 
when  the  heat  is  then  increased  a  sudden  and  copious  evolution 
of  "red  fumes"  results  when  the  dark  colored  compound  is  de- 
composed, and  the  liquid  at  once  becomes  lighter  in  color.  Should 
more  ferrous  sulphate  be  added  before  that  decomposition  has 
taken  place  and  while  the  solution  is  still  dark,  or  should  the 


IRON     TERSULPHATE.  445 

ferrous  sulphate  be  added  all  at  once,  or  too  rapidly,  the  efferves- 
cence, suspended  for  a  while,  may  suddenly  take  place  with  such 
violence  as  to  cause  the  liquid  to  boil  over.  Hence  the  liquid 
should  be  heated  after  each  addition  of  ferrous  sulphate  until  the 
dark  color  disappears  before  any  more  ferrous  sulphate  is  added, 
and  finally  the  product  must  be  heated  until  reddish-brown  instead 
of  brownish-black  and  until  free  from  nitrous  odor. 

When  a  few  drops  of  the  solution  is  added  to  a  little  freshly 
prepared  test-solution  of  potassium-ferricyanide  there  should  be 
no  blue  coloration  or  precipitate  but  at  most  only  a  greenish- 
brown  coloration.  This  test  proves  the  absence  of  ferrous  salt. 

The  solution  of  ferric  sulphate  (U.  S.  P.),  when  completely 
precipitated  with  an  excess  of  ammonia  water  (10%),  yields  about 
14.84  per  cent  of  ferric  hydroxide.  Compared  with  solution  of 
ferric  chloride  (U.  S.  P.),  100  parts  of  solution  of  ferric  sulphate 
contains  the  same  amount  of  iron  as  61.73  parts  of  solution  of 
ferric  chloride. 

Description. — A  clear,  dark,  red-brown  liquid,  almost  odorless 
(having  at  most  a  very  faint  odor  from  traces  of  free  nitric  acid)  ; 
taste  strongly  styptic,  acid.  Reaction  acid.  Sp.  w.  about  1.320 
at  15°. 

On  slowly  mixing  2  volumes  of  the  solution  with  i  volume  of 
concentrated  sulphuric  acid,  in  a  beaker,  no  solid  white  mass  will 
separate  on  standing  (difference  from  snbsulphate). 

The  "liquor  ferri  persulphatis"  or  "solution  of  ferric  sulphate" 
of  the  British  Pharmacopoeia  is  stronger  than  the  American 
preparation.  It  has  the  sp.  w.  1.441  and  contains  about  36.19 
per  cent  of  anhydrous  ferric  sulphate,  corresponding  to  about 
10.09  Per  cent  °f  metallic  iron.  Thus  1,000  Gm  of  the  American 
"solution  of  ferric  sulphate"  exactly  equals  793  Gm  of  the  British 
"solution  of  ferric  sulphate." 

IRON    ALUM. 

FERRI    ET    AMMONII    SULPHAS. 

[Sulphate  of  Iron  and  Ammonium.      Iron  Alum.] 
FeH4N(SO4)2.i2H2O=482. 

Solution  of  normal  ferric  sulphate 300  ml 

Ammonium    sulphate 40  Gm 

Diluted  sulphuric  acid 30  ml 


446  IRON  ALUM. 

Heat  the  iron  solution  to  the  boiling  point ;  add  the  ammonium 
sulphate,  and,  when  this  has  dissolved,  add  the  acid.  Stir  well. 
Set  the  mixture  aside  in  a  well  covered  vessel,  in  a  cool  place,  for 
a  day  or  two.  Remove  the  crystals  from  the  mother  liquor,  wash 
them  hastily  with  a  little  cold  water,  dry  them  at  once  by  pressing 
them  gently  between  blotting  paper,  and  put  them,  without  delay, 
in  a  bottle,  which  must  be  tightly  stoppered  and  kept  in  a  cool 
place. 

The  crystals  should  be  clean,  well  developed,  and  of  a  hand- 
some violet  color. 

Reaction. 

Fe2(SO4)3+(H4N)2SO4+24H2O=2FeH4N(SO4)2.i2H2O. 

Notes.  The  sulphuric  acid  is  added,  because  good  crystals  are 
best  obtained  when  a  slight  excess  of  acid  is  present.  If  there 
is  a  deficiency  of  acid  the  crystals  will  be  brownish,  unclear,  or 
very  pale. 

The  color  of  the  crystals  of  iron  alum  varies  materially;  it  is 
sometimes  bluish  or  purplish,  sometimes  violet,  and  sometimes 
a  pale  rose  color.  Crystals  which  are  purplish  violet  may  become 
almost  devoid  of  color  upon  recrystallization  from  a  water-solu- 
tion unless  the  solution  is  rendered  decidedly  acid  by  the  addition 
of  H2SO4. 

[Crystals  of  common  alum  grow  in  a  saturated  solution  of  iron 
alum.  Large,  clear,  well  defined  crystals  can  thus  be  made  which 
have  a  colorless  center  enveloped  in  a  beautifully  colored  exterior. 
This  is  an  interesting  .experiment  for  students  to  make,] 

Description. — A  violet  colored  salt,  resembling  alum  in  crystal- 
line form,  insoluble  in  alcohol,  readily  soluble  in  water,  giving  a 
brown  solution. 

Re  crystallized  Iron  Alum. 

Iron  alum,  when  effloresced,  discolored,  or  otherwise  unsightly, 
may  be  recrystallized  as  follows : 

Iron   alum 100  parts 

Water    300  parts 

Diluted  sulphuric  acid 10  parts 

Dissolve  the  salt  in  the  acidified  water  with  the  aid  of  heat, 
filter  the  solution,  and  crystallize  in  the  usual  way. 


IRON  SULPHIDE.  447 

IRON  (FERROUS)  SULPHIDE. 

FERRI    SULPHIDUM. 

FeS=88. 

Metallic  iron  in  the  form  of  wire,  filings, 

turnings  or  scraps 7  parts 

Sulphur   4  parts 

Heat  together  in  an  earthenware  crucible  until  fused. 
Reaction.     Fe+S=FeS. 

Description. — Heavy,  black,  lustreless,  odorless  pieces  or 
masses,  readily  soluble  in  hydrochloric  acid  with  copious  evolu- 
tion of  hydrogen  sulphide. 

IRON    TANNATE. 

FERRI    TAN N AS. 

Solution  of  ferric  acetate 10  parts 

Tannic  acid 10  parts 

Distilled  water,  sufficient. 

Mix  the  solution  of  acetate  of  iron  with  35  parts  of  distilled 
water,  and  dissolve  the  tannin  in  75  parts  of  distilled  water. 
Filter  the  liquids. 

Add  the  tannin  solution  slowly  to  the  iron  solution,  stirring 
constantly. 

Wash  the  precipitate  and  dry  it. 

Description. — An  odorless  and  tasteless,  insoluble  black  powder. 
IRON  (FERRIC)  VALERATE. 

FERRI   VALERIANAS. 

Fe(C5H902)3=359. 

Sodium  valerate 5  parts 

Solution  of  ferric  chloride,  U.  S 6  parts 

Distilled  water. 

Dissolve  the  sodium  valerate  in  60  parts  of  distilled  water  and 


448  IRON    VALERATE. 

filter.  Mix  the  solution  of  ferric  chloride  with  100  parts  of  dis- 
tilled water.  Add  the  iron  solution  gradually  to  the  solution  of 
sodium  valerate,  stirring  well,  taking  care  to  discontinue  the  ad- 
dition of  ferric  chloride  as  soon  as  it  no  longer  causes  precipitation. 
Collect  the  precipitate  on  a  filter  and  wash  it  quickly  with  cold 
distilled  water  until  the  washings  are  tasteless.  Dry  the  product 
on  blotting  paper  frequently  changed  and  without  the  aid  of  heat. 
Keep  the  product  in  small,  tightly  closed  bottles  in  a  cool,  dark 
place. 

Reaction. 

FeQ3+3NaC5H9O2=Fe  ( C5H9CX  )  3+3NaCl. 

Description. — A  brick-red,  or  reddish  brown  powder  having 
an  odor  of  valeric  acid.  Decomposed  by  boiling  water.  Soluble 
in  alcohol. 

LEAD   ACETATE. 

PLUMBI    ACETAS. 

Pb(C2H802)2.3H20:=378.5. 

(Sugar  of  Lead.) 

Litharge 5  parts 

Acetic  acid 8  parts 

Water 4  parts 

Mix  the  litharge,  acid  and  water  in  a  porcelain  dish.  Stir  well. 
Let  stand  a  day.  Then  heat  over  a  water-bath  until  the  oxide 
is  dissolved.  Filter.  Evaporate  until  a  pellicle  forms,  and  then 
set  aside  to  cool  and  crystallize,  adding  first,  if  necessary,  a  little 
more  acetic  acid  to  impart  to  the  solution  a  decidedly  acid  reac- 
tion. Collect  the  crystals,  drain  and  dry  them,  immediately  put 
the  product  in  dry  bottles,  close  these  tightly,  and  keep  them  in 
a  cool  place. 

Reaction. 
PbO+2HC2H3O2+2H2O=Pb(C2H,O,)2.3H2O. 

Notes.  The  acetic  acid  dissolves  the  lead  oxide  without  the 
aid  of  heat  if  sufficient  time  is  allowed.  But  the  solution  is 


LKAD  ACETATE.  449 

greatly  hastened  by  the  application  of  moderate  heat.  Too  high 
a  temperature  would  cause  a  loss  of  acetic  acid. 

Should  the  solution  have  a  green  color  this  shows  the  presence 
of  copper  which  is  sometimes  contained  in  litharge.  To  remove 
this  copper  place  a  strip  of  pure  lead  in  the  solution ;  the  copper 
is  then  deposited  upon  the  lead  and  may  be  scraped  off  after  which 
the  bright  clean  lead  is  again  placed  in  the  solution.  This  must 
be  repeated  as  long  as  any  copper  deposits  upon  the  lead.  When 
the  rKquid  is  free  from  copper,  add  a  little  more  acetic  acid,  // 
necessary,  to  render  the  solution  decidedly  acid  in  its  reaction  on 
test-paper. 

When  too  concentrated,  solutions  of  lead  acetate  can  not  easily 
be  filtered  through  paper.  Should  the  solution  be  found  too  con- 
centrated (by  evaporation)  to  pass  through  the  paper  filter 
readily,  dilute  it  with  distilled  water. 

Should  the  crystals  obtained  contain  iron  acetate  they  will  have 
a  yellowish  or  rusty  color.  The  salt  must  then  be  redissolved 
and  recrystallized  until  colorless. 

When  perfectly  clear  and  colorless  crystals  are  formed  the 
product  is  pure. 

The  mother  liquor  may  be  evaporated  to  one-half  its  volume, 
and,  after  adding  a  little  more  acetic  acid,  set  aside  for  the  forma- 
tion of  an  additional  crop  of  crystals. 

Very  large  crystals  can  be  obtained  by  the  spontaneous  evapora- 
tion of  a  solution  saturated  at  the  temperature  of  the  laboratory; 
but  very  large  crystals  are  not  desirable  for  pharmaceutical  uses. 
Smaller  needle-shaped  crystals  are  to  be  preferred,  and  may  be 
obtained  on  cooling  solutions  saturated  at  an  elevated  tempera- 
ture. Very  small  crystals  are  obtained  by  turbidation ;  but  lead 
acetate  in  very  small  crystals  is  too  liable  to  become  contaminated 
with  carbonate  on  exposure  to  the  air. 

This  salt  must  be  drained  and  dried  as  rapidly  as  possible,  but 
without  the  aid  of  heat,  or  at  a  very  moderate  temperature  for 
the  crystals  are  liable  to  dissolve  in  adhering  mother  liquor  if 
wet,  or  to  effloresce  if  dry. 

When  large  amounts  are  prepared  the  crystals  may  well  be 
drained  on  a  muslin  strainer  and  dried  in  an  atmosphere  of  acetic 
acid  produced  by  sprinkling  a  little  of  the  acid  about  the  drying 
salt.  The  product,  if  the  quantity  is  not  too  large,  may  be  most 
conveniently  and  safely  dried  by  gently  pressing  it  between  blot- 

Vol.    11—29 


45O  LEAD  ACETATE. 

ting  paper,  changing  the  paper  several  times  and  as  soon  as  moist, 
until  the  salt  is  dry. 

Moist  lead  acetate  rapidly  absorbs  carbonic  acid  from  the  air, 
if  exposed,  and  forms  insoluble  carbonate.  The  surface  of  the 
crystals  becomes  white  when  covered  with  carbonate. 

The  salt  also  easily  loses  water  of  crystallization. 

Lead  acetate  must  therefore  be  quite  dry  before  it  is  bottled,  the 
containers  must  be  dry,  quite  rilled,  tightly  closed,  and  put  in  a 
cool  place. 

Purification. 

Commercial  "sugar  of  lead"  may  be  purified  by  re-crystalliza- 
tion. 

Dissolve  60  parts  of  sugar  of  lead  in  80  parts  of  hot  distilled 
water,  add  I  part  of  acetic  acid,  filter  the  solution,  let  it  cool, 
and,  when  cold,  collect  the  crystals.  Evaporate  the  mother-liquor 
to  obtain  further  crops  of  crystals,  and  continue  this  as  long  as 
a  pure  product  is  obtained. 

Collect  and  dry  the  product  as  indicated  in  the  "notes"  above. 

Description. — Colorless,  clear,  crystals  of  a  faintly  acetous  odor, 
and  sweetish,  astringent,  finally  nauseous  metallic  taste.  Ef- 
florescent. Becomes  whitish  on  exposure  to  air  both  from  loss 
of  water  of  crystallization  and  by  the  formation  of  carbonate  due 
to  the  absorption  of  carbon  dioxide  from  the  air. 

Soluble  in  2.3  parts  of  water,  and  in  21  parts  of  alcohol,  at 
15°  ;  in  1.5  parts  of  boiling  water  and  in  I  part  of  boiling  alcohol. 

At  40°  it  loses  its  water  of  crystallization,  which  amounts  to 
14.25  per  cent;  but  it  loses  a  portion  of  its  water  even  at  15°  on 
exposure. 

A  solution  of  10  per  cent  strength,  if  made  with  distilled  water 
which  has  just  been  boiled  to  expel  air  and  carbon  dioxide,  must 
be  almost  if  not  quite  clear. 

Recrystallized  Lead  Acetate. 

Sugar  of  lead 100  parts 

Water 200  paits 

Acetic   acid 5  parts 

Dissolve  the  sugar  of  lead  in  the  water  by  the  aid  of  heat,  add 
the  acetic  acid,  mix  well,  filter,  and  set  the  solution  aside  to 


LEAD  CARBONATE.  451 

crystallize  at  rest.  Collect  and  drain  the  crystals,  press  them 
gently  between  cloths  or  bibulous  paper,  dry  rapidly  in  cold  air, 
and  keep  the  product  in  tightly  closed  bottles. 

Turbidated  Lead  Acetate. 

Sugar  of  lead 30  parts 

Boiling  distilled  water 30  parts 

Acetic   acid i  part 

Dissolve,  filter,  evaporate  over  a  water-bath  to  one-half.  Cool 
the  solution  quickly,  stirring  frequently.  Collect,  drain,  and  dry 
the  crystals  at  the  ordinary  room  temperature  as  quickly  as  pos- 
sible with  the  aid  of  bibulous  white  paper,  frequently  changed. 
Put  the  product  at  once  in  dry  bottles,  close  these  tightly,  and  keep 
them  in  a  cool  place. 

LEAD    CARBONATE. 

PLUMBI    CARBONAS. 

2PbC08.Pb(  OH)  3=773.5. 

Prepared  by  acting  on  sheet  lead  with  acetic  acid,  moisture 
and  carbonic  acid  gas,  until  the  lead  is  consumed  or  covered  with 
a  thick  coat  of  white  lead,  which  is  then  removed,  ground  with 
water,  washed  and  dried.  Or,  carbonic  oxide  is  conducted 
through  solution  of  subacetate  of  lead,  the  precipitate  being  the 
product,  while  the  remaining  liquor  containing  normal  lead  ace- 
tate is  again  converted  into  solution  of  subacetate  of  lead  by 
maceration  with  levigated  litharge. 

White  lead  is  a  basic  carbonate,  as  may  be  seen  from  the 
formula  given  above. 

The  same  lead  carbonate  is  also  obtained  when  lead  nitrate  or 
normal  lead  acetate  is  decomposed  by  sodium  carbonate: 

Lead  nitrate 10  parts 

Sodium  carbonate 9  parts 

Dissolve  the  lead  nitrate  and  the  sodium  carbonate  each  in  100 
parts  of  water,  and  filter  the  solutions  separately.  Pour  the  lead 
salt  solution  into  the  sodium  carbonate  solution,  stirring  con- 
stantly. Wash  the  precipitate  with  hot  water;  collect  and  dry  it. 


452  LEAD  CARBONATE. 

Reaction. 

3Pb  ( N03 )  2+3Na2C03+H20 

=2PbCO3.Pb  ( OH)  2+6NaNO3+CO2. 

Description. — A  heavy,  white  powder,  insoluble  in  water,  but 
soluble  with  effervescence  in  acetic  or  nitric  acid.  Odorless  and 
tasteless. 

LEAD    CHROMATE. 

PLUMBI    CHROMAS. 
PbCr04=322.5. 

(Chrome  Yellow.) 

Lead  nitrate 25  parts 

Potassium    dichromate 1 1  parts 

Water. 

Dissolve  the  lead  salt  in  35  parts  of  hot  water,  filter,  and  dilute 
the  solution  with  30  parts  of  cold  water. 

Dissolve  the  dichromate  in  35  parts  of  hot  water,  filter,  and 
dilute  this  filtrate  with  65  parts  of  cold  water. 

Add  the  dichromate  solution  gradually  to  the  lead  nitrate  solu- 
tion, stirring  well. 

Wash  the  precipitate  by  affusion  and  decantation  of  water  sev- 
eral times  until  the  washings  are  free  from  nitrate.  Collect  the 
lead  chromate  on  a  muslin  strainer,  let  it  drain,  press  out  the 
most  of  the  remainder  of  the  water  with  the  aid  of  a  screw  press, 
break  the  press  cake  into  pieces  and  dry  it  upon  glass  plates  with 
the  aid  of  moderate  heat. 

Reaction. 

2Pb  ( NO3)  2+K2Cr2O7+H2O 

— 2PbCrO4+2KNO8+2HNO8. 

Notes.  There  should  be  as  nearly  complete  decomposition  of 
both  factors  as  possible.  •  Hence  it  is  advisable  not  to  add  all  of  the 
dichromate  solution  to  the  whole  quantity  of  the  lead  salt  at  once. 
Reserve,  instead,  a  small  portion  of  the  solution  of  lead  nitrate; 


LEAD  CH  ROM  ATE.  453 

add  the  dichromate  solution  gradually  to  the  remainder  of  the 
lead  nitrate  until  the  dichromate  is  slightly  in  excess,  which  may  be 
ascertained  by  the  color  of  a  filtered  portion  of  the  mixture,  for 
the  liquid,  on  filtration,  remains  colorless  until  an  excess  of  di- 
chromate has  been  added,  after  which  it  becomes  yellow.  When 
a  filtered  test-portion  is  found  to  be  yellow,  add  cautiously 
enough  of  the  reserved  portion  of  lead  nitrate  solution  to  render 
the  liquid  colorless  again. 

Twenty-five  parts  of  lead  acetate  and  20  parts  of  potassium  di- 
chromate may  be  used  instead  of  25  parts  of  lead  nitrate  and  n 
parts  of  dichromate. 

When  "chrome  yellow"  is  boiled  with  a  dilute  solution  of  so- 
dium hydroxide  it  is  converted  into  "chrome  red,"  which  is 'a 
basic  lead  chromate:  PbCO4.PbO. 

Description. — Chrome  yellow  is  an  orange  yellow  insoluble  pig- 
ment, in  lumps  or  in  powder. 


LEAD    IODIDE. 

PLUMBI    IODIDUM. 
PbI2=459-5- 

Lead  acetate 9  parts 

Potassium   iodide 8  parts 

Acetic   acid I  part 

Dissolve  the  acetate  in  90  parts  of  cold  water,  add  the  acid,  and 

.filter.     Dissolve  the  iodide  in  80  parts  of  cold  water  and  filter. 

Pour  the  lead  salt  solution  into  the  solution  of  potassium  iodide, 

stirring  constantly.     Collect  the  precipitate  on  a  filter  and  wash 

it  with  cold  water.     Dry  it  between  bibulous  paper. 

Reaction.     Pb(C2H3O2)2+2KI=PbI2+2KC2H3O2- 

Notes.  The  addition  of  acetic  acid  to  the  solution  of  lead  ace- 
tate is  to  prevent  the  precipitation  of  white  carbonate  and  yellow- 
ish white  oxyiodide  of  lead.  Lead  iodide  is  not  more  soluble  in 
acetic  acid  than  it  is  in  water. 

Cold  solutions  are  used  not  only  because  lead  iodide  is  soluble 
to  a  considerable  extent  in  hot  water,  but  also  to  obtain  a  more 


454  LEAD  IODIDE. 

finely  divided  product.  When  hot  liquids  are  used  a  portion  of 
the  iodide  is  held  in  solution  until  the  liquid  is  cold,  separating 
gradually  in  crystalline  scales. 

Lead  iodide  is  also  soluble  in  cold  water,  and  thus  there  is 
always  a  slight  loss,  which  is  increased  by  washing.  Hence  the 
quantity  of  water  used  for  washing  the  precipitate  should  be 
limited,  and  the  washing  should  be  performed  on  a  filter  instead  of 
by  decantation. 

The  lead  acetate  solution  must  be  added  to  the  solution  of  the 
iodide,  for  it  is  necessary  to  have  the  latter  present  in  excess  until 
the  liquids  are  mixed.  Should  the  order  of  mixing  be  reversed, 
or  should  the  lead  acetate  be  in  excess,  oxyiodide  of  lead  is 
formed. 

On  the  other  hand,  if  the  potassium  iodide  is  in  too  great 
excess  after  all  the  lead  acetate  has  been  added,  loss  will  be  oc- 
casioned by  the  formation  of  soluble  double  salts  of  the  iodides 
of  lead  and  potassium. 

Potassium  acetate  also  dissolves  lead  iodide. 

To  obtain  a  larger  yield,  lead  nitrate  is  used  instead  of  acetate, 
the  lead  iodide  being  almost  insoluble  in  a  solution  of  potassium 
nitrate.  The  formula  is  then  as  follows : 

Second  Method. 

Lead  nitrate i  part 

Potassium  iodide I  part 

Water,  sufficient. 

Dissolve  the  lead  nitrate  in  8  parts  of  cold  water,  and  the 
potassium  iodide  in  3  parts  of  cold  water.  Filter  the  solutions. 
Add  the  lead  solution  to  the  solution  of  potassium  iodide,  with 
stirring.  Decant  the  mother  liquor  and  throw  it  away.  Collect 
the  precipitate  on  a  filter  and  wash  it  with  cold  water.  Dry  it 
between  bibulous  paper. 

Crystallization.  If  a  crystalline  product  is  desired,  dissolve  the 
washed  and  still  wet  precipitate  by  boiling  it  with  two  hundred 
times  its  weight  of  water,  filter,  and  let  the  solution  cool  very 
slowly.  The  lead  iodide  obtained  from  10  Gm  of  lead  nitrate 
would  require  nearly  three  liters  of  boiling  water  for  its  solution. 
To  obtain  a  small  quantity  of  crystallized  lead  iodide  as  a  speci- 
men, boil  the  precipitate  with  200  times  its  weight  of  water,  filter 


LEAD  NITRATE.  455 

while  hot,  and  set  the  filtrate  aside  to  cool  slowly.     The  undis- 
solved  portion  should  be  reserved  separately. 

Reaction.     Pb  ( NO3 )  2+2KI=2KNO8+PbI2. 

Description. — A  heavy,  bright-yellow  powder ;  odorless  and 
tasteless.  Soluble  in  2,000  parts  of  water  at  15°,  and  in  about 
200  parts  of  boiling  water. 

LEAD    NITRATE. 

PLUMBI    NITRAS. 

Pb(N03)  ,=330.5. 


Lead  oxide,  in  fine  powder 23  parts 

Nitric  acid   (68% ) 20  parts 

Water    100  parts 

Heat  the  oxide,  acid  and  water  together  in  a  porcelain  dish 
until  the  oxide  has  dissolved;  filter  the  solution;  acidify  it  by 
adding  about  0.50  part  of  nitric  acid ;  evaporate  and  crystallize. 

Reaction.     PbO+2HNO8=Pb  ( NO3 )  2+H2O. 

Notes.  If  copper  be  present  in  the  lead  oxide  the  solution  of 
lead  nitrate  will  be  bluish  instead  of  colorless.  Iron  would  make 
it  yellowish.  Copper  may  be  removed  by  precipitation  on  metal- 
lic lead  as  described  in  the  notes  under  plumbi  acetas.  Iron  is 
removed  by  repeated  recrystallizations. 

Clear  crystals  cannot  be  obtained  unless  the  solution  of  lead 
nitrate  is  decidedly  acid ;  hence,  after  saturating  the  nitric  acid 
with  lead  oxide,  a  small  quantity  of  free  nitric  acid  must  be 
added  to  the  solution  before  it  is  set  aside  to  crystallize. 

The  solution  must  also  be  saturated  only  at  the  room  tempera- 
ture, and  the  crystals  formed  by  spontaneous  evaporation  of  the 
cold  solution. 

In  the  absence  of  free  nitric  acid  the  crystals  obtained  will  be 
white  or  opaque ;  also  when  formed  by  cooling  hot  solutions. 

The  mother-liquor  should  be  evaporated  for  more  crystals. 

Commercial  impure  lead  nitrate  may  be  purified  by  recrystal- 
lization  from  a  water  solution  acidified  with  nitric  acid,  any  cop- 
per or  iron  present  being  first  removed  as  already  described. 


456  LEAD  NITRATE. 

Description.- — Colorless,  transparent  crystals,  odorless,  sweetish, 
astringent,  taste  finally  metallic.  Soluble  in  2  parts  of  water  at 
15°  and  in  0.75  part  of  boiling  water.  Insoluble  in  alcohol.  Re- 
action acid. 

Crystallized  Lead  Nitrate. 

Crude  lead  nitrate 10  parts 

Water 20  parts 

Diluted  nitric  acid 3  parts 

Dissolve  the  lead  nitrate  in  the  water  by  the  aid  of  heat,  add 
the  acid,  filter  the  hot  solution,  and  set  it  aside  to  crystallize. 
Collect,  drain,  and  dry  the  crystals,  and  keep  the  product  in  a 
tightly  closed  bottle. 

Notes.  The  crystals  should  be  perfectly  colorless  and  trans- 
parent. If  unclear  or  whitish  they  should  be  redissolved  and  re- 
crystallized  from  a  water-solution  acidified  with  nitric  acid  as 
before. 

LEAD    OLEATE. 

PLUMBI    OLEAS. 

Pb(C18H3302)2=768.5. 

Lead   acetate 100  Gm 

White  castile  soap,  in  fine  powder 165  Gm 

Dissolve  the  lead  acetate  in  ten  liters  of  water;  if  decidedly 
milky,  add  to  it,  gradually,  enough  acetic  acid  to  render  the  solu- 
tion clear,  being  careful  to  avoid  adding  an  excess  of  the  acid. 
Dissolve  the  soap  in  2,500  ml  of  hot  water,  and  add  this  solution 
slowly  to  that  of  the  lead  acetate.  Boil  the  mixture,  reject  the 
mother  liquor,  wash  the  precipitated  oleate  twice  with  boiling 
water,  using  ten  liters  each  time.  Separate  the  water  from  the 
product. 

Reaction. 

Pb(C2H302)2+2NaC18H3302 

=Pb  ( C18H3302)  2+2NaC2H302. 

Notes.     Prepared  in  this  manner  the  lead  oleate  is  a  hard,  brit- 


LEAD  OXIDE.  457 

tie,  white  plaster  when  cold.  The  yield  is  about  160  Gm.  This 
lead  oleate  is  more  hard  and  brittle  than  lead  plaster,  which  is 
made  by  boiling  lead  oxide  with  olive  oil  and  water.  It  contains 
28.95  Per  cent  °f  *eacl  oxide.  Lead  oleate  obtained  by  dissolving 
lead  oxide  in  oleic  acid  is  usually  too  soft  and  sticky.  An  oleate 
of  lead  containing  20  per  cent  of  lead  oxide  dissolved  in  an  excess 
of  oleic  acid  is  readily  obtained  by  digesting  4  parts  of  lead  oxide 
in  fine  powder  with  4  parts  of  oleic  acid  at  about  60°  C,  stirring 
frequently  until  combined,  the  product  being  a  soft  yellowish 
ointment. 

LEAD   OXIDE. 

PLUMBI    OXIDUM. 
PbO=222.5. 

Lead  oxide  is  prepared  on  a  large  scale  by  oxidizing  the  metal 
at  high  temperatures  in  special  furnaces.  The  purity  of  the  prod- 
uct formed  depends  upon  the  purity  of  the  lead  used,  and  the, 
degree  of  oxidation  on  the  temperature  and  the  access  of  air. 
The  color  also  depends  upon  the  temperature  at  the  time  of  oxida- 
tion, and  further  upon  the  subsequent  process  of  cooling.  When 
slowly  cooled  the  lead  oxide  is  yellowish-red ;  but  when  rapidly 
cooled  it  is  reddish-yellow. 

Massicot  is  a  yellow  powder  usually  containing  a  small  amount 
of  "red  lead"  or  "minium."  But  very  pure  lead  oxide  of  this 
kind  can  be  obtained  from  some  of  the  manufacturers  of  paints. 
Massicot  is  PbO. 

Litharge  is  also  PbO,  but  is  obtained  by  the  partial  fusing  to- 
gether of  the  particles  of  the  yellow  massicot.  Litharge  is  either 
yellowish-red  or  reddish-yellow,  varying  considerably  in  the  shade 
of  its  color. 

[Red  lead,  or  minium,  is  not  PbO,  but  Pb3O4  (or  2PbO.PbO,). 
This  oxide  is  also  obtained  by  the  oxidation  of  the  metal,  or  by 
carefully  heating  litharge  in  a  plentiful  supply  of  air.] 

Lead  oxide,  PbO,  may  be  made  by  heating  lead  nitrate  or  lead 
carbonate  until  completely  decomposed.  The  residue  is  the 
oxide.  When  pure  lead  nitrate  is  employed  a  very  pure  lead 
oxide  is  obtained  if  the  heat  be  continued  until  red  vapors  cease 
to  be  given  off  and  the  residue  acquires  a  constant  weight.  The 


458  LEAD  OXIDE, 

nitrate  should  first  be  powdered,  the  heat  gradually  increased,  and 
the  powder  stirred. 

Should  the  residue  be  partly  yellow  and  partly  red,  as  it  always 
will  be  if  not  thoroughly  stirred  or  mixed,  it  is  triturated  until 
of  perfectly  uniform  color. 

Pure  lead  oxide  is  completely  soluble  in  solution  of  normal  ace- 
tate of  lead. 

LEAD    PEROXIDE. 

PLUMBI   PEROXIDUM. 
Pb02=238.5. 

Lead   nitrate 5  parts 

Chlorinated   lime 8  parts 

Water. 

Dissolve  the  lead  salt  in  30  parts  of  hot  water.  Triturate  the 
chlorinated  lime  well  with  60  parts  of  cold  water  and  strain.  Add 
the  chlorinated  lime  solution  in  portions  to  the  hot  lead  salt  solu- 
tion in  a  dish,  stirring  well.  When  about  one-half  of  the  solution 
of  chlorinated  lime  has  been  added,  heat  the  mixture  until  the 
light  colored  precipitate  turns  dark-brown.  Then  filter  about 
10  ml  of  the  liquid  and  test  it  by  adding  a  little  of  the  chlorinated 
lime  solution  and  warming. 

If  a  precipitate  is  formed,  add  more  chlorinated  lime  solution 
to  the  mixture  in  the  dish.  Test  again  from  time  to  time  in  the 
same  way  until  no  further  precipitation  is  caused  by  the  chlorin- 
ated lime.  Then  heat  the  mixture  nearly  to  the  boiling  point, 
stirring  well.  Let  settle,  and  wash  the  precipitate  with  boiling 
water,  by  decantation,  until  the  washings  are  tasteless  or  free 
from  chloride  or  nitrate.  Collect  and  dry  the  peroxide.  . 

Reaction. 

Pb(NO3)2+2Ca(ClO)2+H2O 

=PbO2+CaCl2+Ca(NO8)2+2HCl+2O. 
Description. — A  heavy,  dark-brown,  insoluble  powder. 


LEAD  TAN  NATE.  459 

LEAD    TANNATE. 

PLUMBI    TANNATUM. 

Lead  acetate 8  parts 

Tannic   acid 9  parts 

Distilled  water,  sufficient. 

Dissolve  the  lead  acetate  and  the  tannic  acid,  each,  separately, 
in  ten  times  its  weight  of  distilled  water.  Add  enough  of  the 
tannin  solution  to  the  lead  solution  to  precipitate  the  lead  in  the 
form  of  tannate,  discontinuing  the  addition  of  the  tannic  acid 
whenever  it  ceases  to  produce  further  precipitation. 

Wash  the  precipitate  with  distilled  water  until  the  washings 
no  longer  give  an  acid  reaction  on  test-paper.  . 

Dry  the  product  with  the  aid  of  gentle  heat. 

Description. — A  grayish-yellow,  odorless,  tasteless,  insoluble 
powder. 

The  substantive  noun  "tannatum"  is  used  instead  of  tannas  to 
indicate  that  the  composition  is  indefinite. 

GLYCERITE    OF   TANNATE   OF   LEAD. 

Oak  bark,  in  coarse  powder 175  Gm 

Glycerin   35  Gm 

Solution  of  subacetate  of  lead,  sufficient. 
Water,  sufficient. 

Boil  the  bark  with  two  liters  of  water  for  fifteen  minutes. 
Strain.  To  the  colature  add  gradually  solution  of  subacetate  of 
lead  so  long  as  a  precipitate  continues  to  be  formed.  Collect  the 
precipitate  on  a  wetted  muslin  strainer  and  wash  it  with  water 
until  the  washings  are  tasteless.  Let  drain,  and  press  the  magma 
between  bibulous  paper  until  enough  of  the  moisture  has  been 
removed  from  it  to  reduce  its  weight  to  65  Gm.  Mix  this  while 
still  moist  with  the  glycerin. 

LEAD    PLASTER. 

EMPLASTRUM    PLUMBI. 

[Diachylon  Plaster.] 

Lead   oxide 32  parts 

Olive  oil 60  parts 

Water. 


460  LEAD  PLASTER. 

Mix  the  lead  oxide,  previously  passed  through  a  No.  80  sieve, 
intimately  with  about  one-half  of  the  olive  oil,  by  tritnration, 
and  add  the  mixture  to  the  remainder  of  the  oil  contained  in  a 
bright  copper  kettle  of  a  capacity  equal  to  at  least  four  times  the 
bulk  of  the  ingredients.  Then  add  10  parts  of  boiling  water,  and 
boil  the  whole  together,  over  a  fire,  constantly  stirring  with  a 
wooden  spatula,  until  a  small  portion,  when  dropped  into  cold 
water,  is  found  to  be  pliable  and  tenacious.  From  time  to  time 
add  a  little  water  to  replace  that  lost  by  evaporation.  When  the 
mixture  in  the  kettle  has  acquired  a  whitish  color  and  is  per- 
fectly homogeneous,  transfer  it  to  a  vessel  containing  warm 
water,  and  as  soon  as  the  mass  has  sufficiently  cooled,  knead  it 
well  with  the  water  so  as  to  remove  the  glycerin,  renewing  the 
water  from  time  to  time,  as  long  as  it  may  be  necessary.  Finally 
divide  the  mass  into  rolls  of  suitable  size. 

Description. — A  yellowish-white,  tenacious  plaster. 

Another  Method  (G.  P.) 

Lead   oxide 100  parts 

Olive  oil ioo  parts 

Lard ioo  parts 

Water. 

Mix  the  oil  and  lard  by  melting  them  together.  Add  the  lead 
oxide  previously  sifted  and  then  well  mixed  with  20  parts  water. 
Boil  the  mixture,  stirring  well  and  uninterruptedly  with  a  wooden 
spatula.  Add  from  time  to  time  about  3  parts  of  hot  water  to  re- 
place that  lost  by  evaporation.  Continue  the  boiling  until  the 
plaster  is  formed  and  all  red  color  has  disappeared. 

See  also  directions  in  the  method  first  described. 

Notes.  Lead  plaster  made  with  olive  oil  alone  (without  lard) 
is  softer  than  that  made  with  olive  oil  and  lard,  because  the 
former  plaster  contains  principally  lead  oleate  with  but  little 
stearate,  while  the  latter  contains  a  greater  proportion  of  stearate. 
The  constituents  of  the  lead  plaster  are  oleate,  palmitate,  stearate 
and  arachate  of  lead. 

The  lead  oxide  does  not  react  readily  with  oil  or  fat  except  at  a 
very  high  temperature  and  in  the  presence  of  water.  In  the 
absence  of  water  a  plaster  can  be  made  but  only  at  so  high  a 


LEAD  PLASTER.  461 

temperature  that  some  of  the  fixed  oil  is  decomposed,  and  a  dark 
plaster  having  a  peculiar  odor  is  then  formed. 

The  heat  must  not  be  too  high.  If  the  plaster  mass  bubbles 
or  spatters  violently  when  water  is  added,  this  proves  that  the 
temperature  is  excessive.  To  avoid  boiling  over,  or  dangerous 
spattering  and  the  burning  of  the  product,  the  kettle  should  be 
taken  from  the  fire  (when  the  addition  of  hot  water  causes  much 
commotion),  the  contents  should  then  be  diligently  stirred,  and 
a  small  amount  of  hot  water  added.  The  kettle  may  then  be  re- 
placed. As  long  as  the  mass  foams  quietly  and  no  irritant  vapors 
arise  there  is  enough  water  present ;  but  when  the  hot  mass  ceases 
foaming  more  hot  water  must  be  added.  Otherwise  the  plaster 
rapidly  gets  too  hot  and  may  be  darkened. 

Diligent  and  vigorous  stirring  with  a  broad  wooden  spatula 
is  necessary  throughout  the  whole  process  of  emplastrification, 
and  it  should  be  effected  in  such  a  manner  that  the  heavy  lead 
oxide  may  be  uniformly  distributed  through  the  mixture  and  not 
permitted  to  settle  to  the  bottom  of  the  kettle. 

As  long  as  the  plaster  mass  retains  any  reddish  tint  there  is 
still  some  lead  oxide  uncombined,  and  the  boiling  must  be  con- 
tinued until  that  tint  has  given  place  to  a  whitish  color. 

Steam  heat  under  pressure  may  be  employed,  but  the  process 
requires  longer  time.  Direct  fire  under  the  kettle  or  dish  is  more 
satisfactory.  But  the  process  of  boiling  lead  plaster  always  occu- 
pies several  hours  even  with  the  employment  of  direct  heat  over 
a  good  fire. 

After  the  glycerin  has  been  washed  out  of  the  plaster  by  knead- 
ing it  with  water,  the  product  should  be  heated  sufficiently  to  ex- 
pel the  water  mixed  with  it. 

To  improve  its  color  it  may  be  "pulled"  while  sufficiently  plastic, 
afterwards  rolled  into  cylindrical  sticks  on  a  plaster  board  kept 
moist  with  a  slight  amount  of  water,  the  hands  of  the  operator 
being  also  kept  moistened. 

LEAD  SUBACETATE  SOLUTION. 

LIQUOR    PLUMBI    SUBACETATIS;    U.    S. 

(Goulard's  Extract.) 

A  water  solution  containing  about  50  per  cent  of  basic  lead 
acetate,  having  the  composition  HOPbC2H3O2=282.5.  [This  is 


42  LEAD  SUBACETATE. 

equivalent  to  about  24.2  per  cent  of  Pb2O(C2H3O2)2,  which  is 
the  composition  assigned  to  the  basic  lead  acetate  contained  in 
this  solution  by  the  definition  given  in  the  American  Pharma- 
copoeia.] 

Lead  acetate 17  parts 

Lead  oxide,  in  fine  powder 10  parts 

Distilled  water. 

Heat  70  parts  of  distilled  water  to  boiling.  Dissolve  the  lead 
acetate  in  the  hot  water.  Transfer  the  solution  to  a  bottle.  Add 
the  previously  sifted  lead  oxide,  in  small  portions,  shaking  well 
and  frequently  after  each  addition  to  prevent  the  oxide  from 
caking  together,  and  waiting  after  each  addition  until  the  portion 
added  has  been  dissolved  before  adding  another  portion.  When 
all  of  the  lead  oxide  has  been  added  and  dissolved,  add  enough 
distilled  water  to  make  the  total  product  weigh  100  parts,  and 
filter  the  solution  through  paper  in  a  well  covered  funnel. 

Keep  the  product  in  well-stoppered  bottles. 

Reaction. 
Pb(C2H8O2).3H2O+PbO=2HOPbC2H,O2+2H2O. 

Notes.  The  lead  acetate  must  be  in  good  condition — i.  e.,  in 
transparent  crystals  containing  the  full  amount  of  water  of  crys- 
tallization and  free  from  carbonate.  The  lead  oxide  also  must  be 
free  from  carbonate  and  from  minium  and  other  impurities.  Un- 
less these  conditions  are  observed  the  solution  can  not  have  the 
required  strength,  for  lead  carbonate  and  minium  are  not  soluble 
in  a  solution  of  lead  acetate.  For  the  same  reason  the  distilled 
water  should  be  boiled  to  expel  carbon  dioxide.  After  making  the 
solution  of  lead  acetate  with  the  hot  water,  it  is  not  necessary  to 
longer  maintain  the  high  temperature.  It  is  usually  directed  that 
the  solution  of  acetate  be  boiled  with  the  oxide ;  but  the  lead  oxide 
dissolves  as  well  even  in  a  cold  solution. 

Several  basic  lead  acetates  are  known,  differing  as  to  their  sol- 
ubility as  well  as  their  percentage  of  lead.  All  are  prepared  by 
dissolving  lead  oxide  in  a  solution  of  lead  acetate,  the  only  dif- 
ference being  the  proportion  of  oxide  added.  Different  pharma- 
copoeias, moreover,  prescribe  different  proportions  of  water.  The 
strength  of  the  solution  obtained  can  not  be  reliably  determined 


LEAD  SUBACETATE.  463 

from  the  proportions  of  the  materials,  but  will  always  be  less  than 
theory  indicates,  for  there  is  always  an  undissolved  white  powder 
remaining,  which  consists  of  carbonate. 

The  molecular  weights  of  lead  acetate  and  lead  oxide  (378,5 
and  222.5)  are  m  tne  proportion  of  17  to  10;  378.5  parts  of  lead 
acetate  and  222.5  parts  of  lead  oxide  form  565  parts  of 
HOPbC2H3O2,  which  would  make  2260  parts  of  solution  of  25 
per  cent  strength  (that  is,  25  per  cent  of  HOPbC2H3O2,  having 
the  molecular  weight  282.5).  The  exact  quantity  of  solution 
which  should  be  obtained  from  17  parts  of  lead  acetate  and  10 
parts  of  lead  oxide  would  be  102  parts.  But  only  100  parts  of 
solution  are  directed  to  be  prepared  from  17  parts  of  acetate  and 
10  parts  of  oxide.  With  such  approximately  pure  materials  as 
may  be  obtained  without  any  difficulty,  a  product  containing  fully 
25  per  cent  of  HOPbC2H3O2  [or  Pb(C2H3O2)2.Pb(OH)2.]  re- 
sults from  the  formula  given. 

The  proportions  ordered  by  the  British  Pharmacopoeia  are  250 
Gm  of  lead  acetate  and  175  Gm  of  lead  oxide  to  make  1,000  ml 
of  product  (or  1,275  Gm). 

The  German  Pharmacopoeia  orders  3  parts  of  lead  acetate,  i 
part  of  lead  oxide,  and  10  parts  of  water. 

The  Pharmacopoeia  of  Norway  prescribes  17  parts  of  lead  ace- 
tate, 5  parts  of  lead  oxide,  and  78  parts  of  water. 

Bottles  containing  solution  of  subacetate  of  lead  soon  become 
coated  with  lead  carbonate,  which  forms  a  white  crust  on  their 
sides.  This  white  crust  is  most  readily  removed  by  nitric  acid. 

The  preparation  becomes  whitish  on  dilution  with  water  con- 
taining carbonic  acid,  sulphates,  etc.,  and  can  be  diluted  so  as 
to  form  a  clear  liquid  only  with  distilled  water. 

Description. — A  colorless  solution  with  a  sweetish  taste  and 
alkaline  reaction.  Sp.  gr.  about  1.237. 

Glycerite  of  Subacetate  of  Lead. 

GLYCERITUM    PLUMBI    SUBACETATIS. 

Lead   acetate 250  Gm 

Lead  oxide,  in  fine  powder 175  Gm 

Glycerin i  ,000  Gm 

Distilled   water.  .  600  ml 


464  LEAD  SUBACETATE. 

Mix  in  a  porcelain  dish  and  boil  the  mixture  fifteen  minutes. 
Filter  and  evaporate  the  filtrate  to  1,000  ml. 

Notes.  This  solution  will  bear  dilution  with  distilled  water, 
yielding  a  clear  liquid.  It  has  about  the  same  strength  as  the 
official  solution  of  subacetate  of  lead. 

Diluted  Solution  of  Lead  Subacetate. 

LIQUOR    PLUMBI    SUBACETATIS   DILUTUS ;    U.    S. 

(Aqua  Saturni.      Lead  Water.) 

Mix  30  ml  of  solution  of  lead  subacetate  with  970  ml  of  distilled 
water,  previously  boiled  and  allowed  to  cool  again. 

LITHIUM    BENZOATE. 

LITHII    BENZOAS. 
LiC7H5O2=T28. 

Lithium  carbonate 3  parts 

Distilled   water 30  parts 

Benzoic  acid 10  parts 

Put  the  lithium  carbonate  and  water  into  a  porcelain  dish  placed 
over  a  water-bath,  warm  gently,  and  add  the  benzoic  acid  gradu- 
ally. When  solution  has  been  effected  filter  the  liquid  and  evapor- 
ate the  filtrate  until  a  moist  crystalline  mass  remains.  Dry  the 
mass  at  a  temperature  of  about  30°  C. 

Reaction. 

Li2CO3+2HC7H5O2=2LiC7H5O2+H2O+CO2. 

Description. — A  white  crystalline  salt,  either  odorless  or  of  a 
faint  benzoin  odor,  and  cooling  sweetish  taste.  Soluble  in  4  parts 
of  water  at  15°  C.  and  in  12  parts  of  alcohol;  and  in  2.5  parts 
boiling  water. 


LITHIUM    BROMIDE.  465 

LITHIUM    BROMIDE. 

LITHII    BROMIDUM. 


Prepared  by  four  different  methods  : 

(i)  By  neutralizing  hydrobromic  acid  with  lithium  carbonate. 
(2)  By  double  decomposition  between  lithium  sulphate  and  po- 
tassium bromide,  the  potassium  sulphate  being  separated  by  the 
addition  of  alcohol  in  which  potassium  sulphate  is  insoluble  while 
the  lithium  bromide  is  soluble.  (3)  By  treating  a  solution  of  fer- 
rous bromide  with  lithium  carbonate.  (4)  From  lithium  sulphate 
and  barium  bromide. 

The  solution  is  evaporated  to  dryness. 

Description.  —  A  white,  granular  salt;  odorless;  taste  sharp, 
bitterish.  Deliquescent.  Soluble  in  0.6  part  of  water  at  15°, 
and  in  one-half  that  proportion  of  boiling  water.  Readily  solu- 
ble also  in  alcohol  and  in  ether.  Neutral  to  litmus  paper. 

LITHIUM    CARBONATE. 

LITHII    CARBONAS. 

Li2C03=  74. 

A  white,  odorless  powder  of  alkaline  taste  and  reaction.  Solu- 
ble in  80  parts  of  water  at  15°,  and  in  140  parts  of  boiling  water. 

Insoluble  in  alcohol. 

[The  solubility  of  lithium  carbonate  in  cold  and  in  boiling  water 
is  variously  stated  by  different  authorities.] 

LITHIUM    CHLORIDE. 

LITHII     CHLORIDUM. 


Neutralize  diluted  hydrochloric  acid  with  lithium  carbonate, 
filter  the  solution,  and  evaporate  to  dryness,  stirring  constantly 

Vol.    11-30 


466  LITHIUM  CITRATE. 

toward  the  close  of  the  evaporation  so  as  to  obtain  a  granulated 
product. 

Description. — A  white,  granular  powder ;  odorless  ;  taste  saline. 
.Readily  soluble  in  water  and  in  alcohol.    Neutral  in  reaction. 


LITHIUM  CITRATE. 

«• 

LITHII     CITRAS. 

Li3C6H5O74H2O=282. 

Lithium  carbonate    ..............  .....     8  parts 

Citric  acid    ..........................    15  parts 

Distilled  water  ................  .......   60  parts 

Dissolve,  filter,  and  evaporate  to  crystallization,  or  until  a  gran 
ular  salt  remains.    Dry  the  product  with  the  aid  of  gentle  heat. 
Keep  it  in  tightly  closed  bottles. 

Reaction.    3Li2CO3+2H3C6H5O7+5H2O 


Description.  —  A  white  crystalline  or  granular  powder  ;  odorless  ; 
taste  faintly  alkaline,  cooling.  Hygroscopic  in  moist  air.  Soluble 
in  2  parts  of  water  at  15°,  and  in  one-half  its  weight  of  boiling 
water.  Insoluble  in  alcohol  and  in  ether. 

Effervescent   Lithium    Citrate. 

Lithium  carbonate  ....................     7° 

Sodium  bicarbonate  ...................   280  Gm 

Citric  acid  ...........................   370  Gm 

Sugar,  in  fine  powder,  a  sufficient  quantity. 

Triturate  the  citric  acid  with  about  200  Gm  of  sugar,  and  dry 
the  mixture  thoroughly.  Then  incorporate  with  it,  by  trituration, 
the  lithium  carbonate  and  sodium  bicarbonate,  and  enough  sugar 
to  make  the  product  weigh  1000  Gm  . 

It  may  be  granulated  in  the  same  way  as  effervescent  magnes- 
ium citrate. 

Keep  the  powder  in  well-stoppered  bottles. 


LITHIUM    IODIDE.  467 

Description.  —  A  white,  coarsely  granular  powder,  readily  sol- 
uble in  water,  with  effervescence,  forming  an  acidulous  solution. 

LITHIUM     IODIDE. 

LITHII     IODIDUM. 


Prepared  by  double  decomposition  between  calcium  iodide  and 
lithium  carbonate,  which  are  heated  together  in  water.  CaI2+ 
Li2CO3^2LiI-j-CaCO3.  It  may  also  be  made  from  iron,  iodine 
and  lithium  carbonate,  in  a  manner  similar  to  the  process  for  pre- 
paring lithium  bromide  from  iron,  bromine  and  lithium  carbonate. 

The  solution  is  evaporated  to  dryness. 

Description.  —  A  white  granular  salt;  odorless;  taste  acrid,  bit- 
terish; deliquescent.  Freely  soluble  in  water,  alcohol,  and  ether. 

LITHIUM    PHOSPHATE. 

LITHII      PHOSPHAS. 
Li2HP04=I03. 

Lithium  chloride  .....................     4  parts 

Sodium  phosphate  ....................    17  parts 

Water. 

Dissolve  the  salts,  each  in  150  parts  of  water,  filter  the  solutions, 
and  pour  the  lithium  chloride  solution  into  the  other,  stirring  well. 
Collect  the  precipitate  on  a  filter  and  wash  it  with  cold  water. 

Reaction.    Na2HPO4+2LiCl=Li2HPO4+2NaCl. 

Description.  —  An  insoluble  white  powder,  odorless  and  taste- 
less. 

LITHIUM   SALICYLATE. 

LITHII     SALICYLAS. 

LiC7H5O3=i44. 

Salicylic  acid   ........................  75  parts 

Lithium  carbonate, 

Distilled  water,  of  each  sufficient. 


LITHIUM   SALICYLATE. 

Mix  the  salicylic  acid  with  200  parts  of  distilled  water  in  a 
porcelain  dish  and  heat  gently  over  a  water-bath.  Add  the 
lithium  carbonate  gradually,  stirring  well,  until  the  solution  ob- 
tained is  nearly  neutralized  (or  but  feebly,  though  distinctly,  acid 
in  reaction).  Filter  the  solution,  and  evaporate  it  to  dryness,  stir- 
ring constantly. 

Keep  it  in  well-stoppered  bottles. 

Reaction.     Li2CO3+2HC7H5Os=2LiC7H5O3.H2O+CO2. 

Notes.  The  quantity  of  lithium  carbonate  required  for  75  parts 
of  salicylic  acid  is  about  20  parts.  The  acid  should  not  be  com- 
pletely neutralized  with  lithium  carbonate;  still  less  should  the 
solution  be  made  at  all  alkaline  for  the  salt  would  then  soon  be- 
come discolored.  The  filter  paper  used  must  be  white  filter  paper, 
entirely  free  from  iron ;  otherwise  the  product  will  be  reddish. 

Description. — A  white,  odorless  powder,  having  a  sweetish, 
somewhat  disagreeable  taste.  Deliquescent  on  exposure. 

Readily  soluble  in  water  and  in  alcohol.  Its  water-solution 
should  have  a  slightly  acid  reaction  on  litmus  paper. 

MAGNESIUM    ACETATE. 

MAGNESII     ACETAS. 
Mg(C2H802)2=I42.2. 

Magnesium  carbonate 40  parts 

Acetic  acid  (36%)    137  parts 

Dissolve  the  carbonate  in  the  acid,  with  the  usual  precautions 
to  prevent  overflowing  on  account  of  the  effervescence.  Heat 
the  liquid  to  expel  carbon  dioxide.  Filter.  Evaporate  to  dryness. 

Description. — A  white,  amorphous,  gummy,  deliquescent  salt. 
Freely  soluble  in  water  and  in  alcohol. 
Must  be  kept  in  tightly  closed  bottles. 

Solution  of  Magnesium  Acetate. 
This  solution  is  said  to  be  an  effective  antiseptic : 

Acetic  acid  (36%) 40  parts 

Magnesium   carbonate    12  parts 

Distilled  water,  sufficient. 


MAGNESIUM  ACETATE.  469 

Heat  the  acetic  acid  gently  in  a  porcelain  dish  over  a  water- 
bath.  Add  gradually  the  magnesium  carbonate  previously  mixed 
with  20  parts  of  distilled  water,  stirring  well.  When  effervescence 
has  ceased,  test  the  solution  on  litmus  paper.  If  found  acid,  add 
enough  magnesium  carbonate  to  exactly  neutralize  it.  Filter,  and 
evaporate  the  filtrate  to  30  parts. 


MAGNESIUM   BOROCITRATE. 

MAGNESII    BOROCITRAS. 

Magnesium  oxide   3  parts 

Boric  acid,  in  powder 3  parts 

Citric  acid,  in  powder TO  parts 

Distilled  water 4  parts 

Mix  the  powders  intimately ;  add  the  water  and  work  the  mix- 
ture into  a  mass.  Let  the  mass  harden ;  then  triturate  it  to  pow- 
der. 

MAGNESIUM   CARBONATE. 

MAGNESII    CARBONAS. 

4MgC03.Mg(OH)2.aq. 

Prepared  from  chloride  or  from  sulphate  of  magnesium  by 
precipitation  with  sodium  carbonate.  The  magnesium  salts  are 
obtained  from  the  "bittern"  of  salt-works.  Magnesium  carbonate 
is  also  manufactured  from  magnesite,  and  from  dolomite,  or  mag- 
nesian  limestone,  by  dissolving  the  magnesium  carbonate  from  the 
powdered  mineral  by  means  of  cold  water  and  carbonic  acid  under 
pressure,  when  magnesium  bicarbonate  is  formed.  The  solution 
is  then  boiled,  when  the  basic  carbonate,  which  constitutes  the 
official  preparation,  is  precipitated. 

In  pharmacy  distinction  is  made  between  "heavy  magnesium 
carbonate"  and  "light  magnesium  carbonate."  The  light  mag- 
nesium carbonate  differs  from  the  heavy  variety  in  these  respects : 
the  light  carbonate  is  about  three  times  as  bulky ;  when  examined 
under  the  microscope,  it  is  found  to  be  partly  amorphous,  but 
containing  numerous  slender  prismatic  crystals,  whereas  the  heavy 
variety  is  wholly  amorphous  and  somewhat  granular;  the  light 
magnesium  carbonate  yields  less  magnesium  oxide  on  calcination. 


47O  MAGNESIUM    CARBONATE. 

These  differences  depend  upon  the  methods  employed  in  the 
preparation  of  the  products.  The  working  formulas  given  in  the 
British  Pharmacopoeia  are  as  follows: 

Light  Magnesium  Carbonate. 

Magnesium  sulphate 25  parts 

Sodium  carbonate   30  parts 

Dissolve  each  salt  in  200  parts  of  cold  distilled  water,  filter,  and 
mix  the  solutions  cold.  Boil  the  mixture  in  a  porcelain  dish  for 
fifteen  minutes.  Transfer  the  precipitate  to  a  wetted  muslin 
strainer,  and  wash  it  with  boiling  distilled  water  until  the  wash- 
ings cease  to  give  a  precipitate  with  test  solution  of  barium 
chloride.  Then  let  the  precipitate  drain,  and  dry  it  at  not  over 
100°  C. 

Heavy  Magnesium  Carbonate. 

Magnesium  sulphate 25  parts 

Sodium  carbonate  30  parts 

Dissolve  the  salts,  each  in  50  parts  of  boiling  distilled  water; 
filter,  and  mix  the  two  solutions  while  hot.  Evaporate  the  mix- 
ture on  a  sand-bath  to  perfect  dryness.  Digest  the'  residue  for 
half  an  hour  with  100  parts  of  boiling  water,  collect  the  precipitate 
on  a  wetted  muslin  strainer,  and  wash  it  repeatedly  with  distilled 
water  until  the  washings  cease  to  give  a  precipitate  with  test  solu- 
tion of  barium  chloride.  Drain  the  product  and  dry  it  at  not  over 


Reaction,    4MgSO4+4Na2CO3+5H2O= 
3MgCO3.Mg(OH)2.4H2O+4Na,SO4+CO2;or  perhaps  5MgSO4 


+C02. 

Notes.  It  will  be  seen  that  the  differences  in  manipulation  are  : 
the  use  of  more  dilute  and  cold  solutions  in  making  the  light 
magnesium  carbonate,  and  the  precipitate  is  in  that  case  simply 
heated  for  fifteen  minutes  with  the  mother  liquor  ;  while,  in  mak- 
ing the  heavy  magnesium  carbonate,  the  solutions  are  four  times 
as  concentrated,  and  mixed  while  hot,  the  mixture  being  then 


MAGNESIUM    CARBONATE.  471 

evaporated  to  perfect  dryness  on  a  sand-bath,  after  which  the 
residue  is  freed  from  sodium  sulphate  by  digestion  and  subsequent 
washing  with  boiling  water. 

When  the  precipitate  is  formed  with  cold  solutions,  it  contains 
rather  less  magnesium  than  if  prepared  with  hot  solutions.  When 
boiled  in  the  liquid  for  a  short  time  carbonic  acid  passes  away ;  in 
preparing  the  light  magnesium  carbonate  the  heating  should  be 
discontinued  as  soon  as  the  evolution  of  carbonic  acid  has  com- 
menced. When  formed  with  hot,  concentrated  solutions,  the  mix- 
ture being  boiled  down  to  dryness,  the  precipitate  contains  less 
carbonic  acid  when  formed,  and  loses  more  of  that  acid  afterwards 
wrhen  exposed  to  the  stronger  heat. 

Composition.  Fritzsche,  Hager  and  Fliickiger  state  that  the 
composition  of  magnesium  carbonate  is4MgCO3.Mg(OH)2.4H2O ; 
the  U.  S.  P.  gives  it  as  4MgCO3.Mg(OH)2.5H2O ;  the  British 
Pharmacopoeia  states  it  as  being  3MgCO3.Mg(OH)24H2O.  That 
there  is  a  difference  in  composition  between  light  and  heavy  mag- 
nesium carbonate  may  be  regarded  as  certain,  although  the  same 
formula  is  given  by  the  British  Pharmacopoeia  for  both.  Light 
magnesium  carbonate  contains  a  greater  proportion  of  true  carbon- 
ate (MgCO3)  and  a  correspondingly  less  proportion  of  hydroxide 
(Mg(OH)2).  The  quantity  of  water  in  the  product  seems  also 
to  vary. 

Description. — Light,  white,  friable  masses,  or  a  light,  white 
powder ;  odorless ;  produces  a  slightly  earthy  feel  in  the  mouth. 
Practically  insoluble  in  pure  water,  although  it  imparts  to  it  a 
slightly  alkaline  reaction.  Insoluble  in  alcohol. 

The  foregoing  description  applies  to  the  light  variety.  The 
heavy  carbonate  is  a  powder  only  one-third  as  bulky. 


MAGNESIUM  CHLORIDE;    CRUDE. 

MAGNESII  CHLORIDUM    CRUDUM. 

MgCl2.6H2O= 203. 

Magnesite,  in  powder   100  parts 

Hydrochloric  acid  (32%  of  HC1) 260  parts 

Magnesium  oxide   i  part 

Water    50  Parts 


472  MAGNESIUM    CHLORIDE. 

Mix  the  magnesite  with  the  water  in  a  large  porcelain  dish ; 
heat  to  about  90°,  and  add  the  acid  in  small  portions  at  a  time, 
stirring  well  and  allowing  the  effervescence  to  subside  after  each 
addition  before  adding  more.  When  all  of  the  acid  has  been 
added  heat  the  liquid  to  90°  for  a  few  minutes.  Neutralize  per- 
fectly with  magnesia.  Add  50  parts  of  water  and  mix  well.  Then 
add  5  parts  of  chlorine  water,  stir  well,  and  keep  the  mixture  hot 
for  about  one  hour.  Filter  while  hot.  Evaporate  the  filtrate  until 
it  has  about  1.30  sp.  w.  while  still  hot.  Then  allow  it  to  cool. 
Collect  and  drain  the  crystals. 

Reaction.     MgCO3+2HCl=MgCl2+H2O+CO2. 

Notes.  The  product  contains  some  calcium  chloride  because 
the  magnesite  contains  calcium  carbonate.  The  solution  of  mag- 
nesium chloride  should  not  be  allowed  to  boil,  as  the  salt  would 
then  be  liable  to  decompose  to  some  extent. 

Description. — Colorless,  deliquescent  crystals,  soluble  in  less 
than  two-thirds  of  their  own  weight  of  cold  water. 

Pure  Magnesium  Chloride. 

May  be  prepared  by  saturating  pure  hydrochloric  acid  with 
pure  magnesium  carbonate,  filtering  the  solution  and  evaporating 
to  crystallization. 


MAGNESIUM    CITRATE. 

MAGNESII     CITRAS. 

Mg3(C6H507)2.aq. 

In  the  Swedish  Pharmacopoeia  occurs  a  magnesium  citrate  of 
the  formula  indicated,  but  mixed  with  an  excess  of  citric  acid 
amounting  to  about  9  per  cent.  It  is  prepared  as  follows : 

Magnesium  carbonate,  in  powder 5  parts 

Citric  acid,  in  fine  powder 8  parts 

Alcohol 12  parts 

Mix  the  magnesium  carbonate  and  acid  intimately  by  tritura- 
tion  in  a  mortar,  and  add  the  alcohol,  mixing  the  whole  well  so 


MAGNESIUM    CITRATE.  473 

as  to  form  a  pasty  mass  free  from  lumps.  Cover  the  mortar  loosely 
with  paper,  and  set  it  aside  until  the  alcohol  has  evaporated,  leav- 
ing a  dry  residue,  which  must  be  at  once  reduced  to  powder. 
Keep  the  product  in  well  stoppered  bottles. 

Reaction.     3  ( 4MgCO3.Mg  ( OH )  2)  +  ioH3C6H5O7= 

5Mg3(C6H507)2+i2C02+i8H20. 

Notes.  To  insure  as  complete  a  chemical  union  as  practicable 
the  citric  acid  might  be  dissolved  in  the  alcohol,  and  the  mag- 
nesium carbonate  added  in  small  quantities  at  a  time.  On  the 
addition  of  the  magnesium  carbonate  the  temperature  of  the  mix- 
ture falls  considerably.  The  mixture  soon  becomes  a  hard  mass 
unless  triturated  without  interruption  until  rendered  perfectly 
homogeneous.  The  carbon  dioxide  escapes  with  effervescence,  and 
the  alcohol  is  added  to  facilitate  the  reaction  and  the  liberation  of 
the  gas.  To  prevent  too  rapid  dissipation  of  the  alcohol,  the  mass 
is  allowed  to  dry  by  spontaneous  evaporation,  and  it  is  better  to 
spread  the  moist  mass  in  an  even  layer  upon  paper  than  to  dry  it 
in  a  heap  in  the  mortar,  because  it  is  essential  that  the  drying  be 
uniform,  otherwise  some  portions  of  the  preparation  become  very 
hard  and  dissolve  with  difficulty  in  water.  A  small  amount  of 
water  must  remain  in  the  product  in  order  to  render  it  readily 
soluble.  It  should,  therefore,  be  dried  only  sufficiently  to  make 
its  pulverization  possible,  and  to  prevent  its  caking  together  after 
being  bottled. 

Description. — A  white  powder,  entirely  but  rather  slowly  soluble 
in  TO  parts  of  water,  requiring  about  10  minutes  to  dissolve.  The 
solution  is  not  permanent,  however,  basic  salts  soon  separating. 
This  decomposition  is  prevented  by  the  presence  of  alkali  citrates. 
An  unclear  solution  may  be  rendered  clear  by  gently  heating  it, 
and  does  not  become  turbid  again  for  several  days. 

Varieties  of  Magnesium  Citrate. — Hager  states  that  normal 
magnesium  citrate  occurs  in  three  forms,  differing  from  each 
other  in  the  proportion  of  water  they  contain,  and  in  solubility. 
Amorphous  magnesium  citrate  contains  2  to  3  molecules  of  water, 
and  is  soluble  in  2  parts  of  water  at  ordinary  temperatures;  meta- 
morphous  magnesium  citrate  contains  about  5  molecules  of  water, 
and  is  soluble  in  10  parts  of  water;  and  the  crystalline  magnesium 


474  MAGNESIUM    CITRATE. 

citrate  contains  7  molecules  of  water,  and  requires  100  parts  of 
water  for  its  solution.  The  amorphous  variety,  when  in  watery 
solution,  gradually  changes  to  the  crystalline  form,  passing 
through  the  metamorphous  form,  this  alteration  being  usually 
completed  in  from  three  to  five  days. 

The  changes  referred  to  are,  at  least  partially,  prevented  by  the 
presence  of  alkali-citrates. 

Effervescent  Magnesium  Citrate. 

Magnesium  carbonate 10  Gm 

Citric  acid 46  Gm 

Sodium  bicarbonate 34  Gm 

Sugar,  in  fine  powder 8  Gm 

Alcohol, 
Distilled  water. 

Mix  the  magnesium  carbonate  intimately  with  30  Gm  of  citric 
acid  and  4  ml  of  distilled  water,  so  as  to  form  a  thick  paste.  Dry 
this  at  a  temperature  not  exceeding  30°  C.  and  reduce  it  to  a  fine 
powder.  Then  mix  it  intimately  with  the  sugar,  the  sodium  bi- 
carbonate, and  the  remainder  of  the  citric  acid  previously  reduced 
to  a  very  fine  powder.  Dampen  the  powder  with  a  sufficient  quan- 
tity of  alcohol,  so  as  to  form  a  mass,  and  rub  it  through  a  No.  6 
tinned-iron  sieve.  Then  dry  it,  and  reduce  it  to  a  coarse,  granular 
powder. 

Keep  the  product  in  well-closed  vessels. 

Notes.  By  reference  to  the  preceding  notes  under  the  title 
Magnesium  Citrate  it  will  be  seen  that  the  first  part  of  'the  process 
has  for  its  object  the  formation  of  acid  magnesium  citrate. 
This  is  then  dried,  powdered,  and  mixed  with  powdered  sugar, 
sodium  bicarbonate  and  citric  acid.  The  citric  acid  must  be  finely 
powdered.  It  is  necessary  that  these  ingredients  should  be  very 
thoroughly  mixed  before  the  alcohol  is  added,  and  only  enough 
alcohol  to  dampen  the  mixture  should  be  used.  The  small  amount 
of  water  contained  in  the  normal  magnesium  citrate  and  in  the 
alcohol  is  sufficient  to  cement  the  particles  of  powder  together 
into  little  granules,  and  the  coarse  powder  is  run  through  a  No. 
6  sieve  to  make  it  more  uniform.  As  a  brass  sieve  would  be  at- 
tacked by  the  compound,  a  tinned  iron  sieve  is  directed  to  be  em- 
ployed. The  sodium  bicarbonate  is  not  decomposed  by  the  citric 


MAGNESIUM    CITRATE. 


475 


acid,  in  the  dry  mixture,  and  hence  the  preparation,  when  dissolved 
in  water,  yields  an  effervescing  drink. 

Description. — A  white,  coarsely  granular  mixture,  deliquescent 
on  exposure  to  air,  inodorous,  having  a  mildly  acidulous  taste  and 
acid  reaction.  Soluble,  with  copious  effervescence,  in  two  parts 
of  water ;  nearly  insoluble  in  alcohol.  The  aqueous  solution  con- 
tains sodium-magnesium  citrate,  some  free  carbonic  acid,  citric 
acid,  and  sugar. 

Solution  of  Magnesium  Citrate. 
Contains  MgHC6H5O7. 

Magnesium  carbonate   15  Gm 

Citric  acid   30  Gm 

Syrup  of  citric  acid , 65  ml 

Potassium  bicarbonate 2.5  Gm 

Dissolve  the  citric  acid  in  120  ml  of  water,  add  the  magnesium 
carbonate,  and  stir  until  dissolved.  Filter  the  solution  into  a 
strong  bottle  of  the  capacity  of  360  ml,  and  containing  the  syrup. 
Then  add  enough  water,  previously  boiled  and  filtered,  to  nearly 
fill  the  bottle,  drop  into  it  the  potassium  bicarbonate,  and  imme- 
diately insert  the  cork,  securing  it  with  twine.  Lastly,  shake  the 
mixture  occasionally  until  the  potassium  bicarbonate  is  dissolved. 

Reaction.  4MgCO3.Mg(OH),+5H3C6H5O7-:5MgHC6H5O7 
+6H2O+4CO2. 

Notes.  Acid  magnesium  citrate,  which  is  contained  in  this  prep- 
aration, does  not  yield  any  deposit  of  magnesium  salt  such  as  is 
formed  after  about  three  days  in  solutions  of  normal  magnesium 
citrate.  As  calcium  citrate  is  insoluble  in  water,  the  magnesium 
carbonate  and  the  water  used  ought  perhaps  to  be  free  from  lime. 
Acid  calcium  citrate  is,  however,  soluble  to  a  limited  extent.  It 
is  directed  in  the  Pharmacopoeial  working  formula  that  the  water 
added  last  shall  be  "previously  boiled  and  filtered."  As  this  pre- 
caution has  for  its  object  the  removal  of  any  lime  present,  the 
same  treatment  should  be  applied  to  the  whole  of  the  water  used, 
if  it  be  intended  that  the  preparation  shall  be  free  from  calcium 
salt,  for  all  of  the  calcium  citrate  formed  from  the  calcium  car- 


476  MAGNESIUM     CITRATE. 

bonate  present  in  the  water  will  dissolve  in  the  excess  of  citric 
acid  used,  unless  the  water  employed  is  quite  "hard,"  in  which 
case  it  is  unfit  for  use. 

The  water  as  well  as  all  other  materials  used  should  be  perfectly 
pure.  Impure  materials  lead  to  the  formation,  sooner  or  later, 
of  slimy  deposits  in  the  product. 

Heat  materially  hastens  the  solution  of  the  acid  and  the  mag- 
nesium carbonate,  and  with  the  quantity  of  citric  acid  taken  no 
harm  will  result  if  the  water  in  which  the  acid  is  dissolved  be  hot, 
and  the  heat  continued  until  the  magnesium  carbonate  has  dis- 
solved. The  solution  should  then  be  filtered,  and  allowed  to  be- 
come quite  cold  before  the  other  ingredients  are  added.  The  clear 
syrup  should  be  first  put  in  the  bottle ;  then  the  filtered  acid  solu- 
tion of  magnesium  citrate  carefully  added  so  as  not  to  mix  it  with 
the  layer  of  syrup  covering  the  bottom  of  the  bottle;  then  the 
bottle  should  be  nearly  filled  with  water,  and  the  potassium  bicar- 
bonate, in  large,  clear  crystals,  dropped  in,  after  which  the  cork 
is  at  once  driven  into  the  neck  of  the  bottle. 

The  bottles  used  for  this  preparation  are  made  strong  enough 
to  bear  the  pressure  caused  by  the  carbonic  acid  liberated  from 
the  potassium  bicarbonate  by  the  citric  acid.  They  must  neces- 
sarily be  of  such  size  as  to  be  nearly  filled  by  the  solution  when 
finished  and  of  proper  strength.  The  corks  used  must  be  about 
I J  inches  long,  and  of  the  finest  quality,  as  large  as  they  can  pos- 
sibly be  used,  and  soaked  in  hot  water  so  as  to  be  soft  and  elastic 
when  inserted ;  the  soaked  corks  ought  to  be  fitted  to  the  necks  of 
the  bottles  when  the  latter  have  been  cleaned,  but  while  still  empty, 
and  should  be  so  large  that,  after  using  the  cork  presser,  they 
can  be  driven  in  by  one  or  two  smart  blows  with  a  mallet,  closing 
the  bottles  perfectly.  The  wire  or  twine  used  to  tie  the  corks  down 
securely  must  be  properly  attached  to  the  necks  of  the  bottles  be- 
forehand, leaving  a  loop  on  one  side  long  enough  to  reach  to  the 
center  of  the  top  of  the  cork,  and  the  two  ends  on  the  opposite  side, 
so  that  as  soon  as  the  cork  has  been  driven  in  rather  more  than 
one-half  its  length,  it  can  be  at  once  tied  over. 

The  quantity  of  potassium  bicarbonate  used  has  been  advan- 
tageously increased  to  2.50  Gm,  so  that  the  solution  may  be  well 
charged  with  carbonic  acid.  The  bottles  should  be  laid  on  their 
sides  in  a  cool  place,  taking  care  not  to  shake  the  contents  so  as 
to  mix  the  syrup  with  the  lighter  watery  solution.  The  potassium 


MAGNESIUM   LACTATE.  477 

bicarbonate  will  then  rest  in  the  syrup,  and  dissolve  but  slowly. 
When  required  for  use,  the  bottle  is  shaken  until  all  of  the  bicar- 
bonate is  dissolved.  Solution  of  citrate  of  magnesium  is  rather 
agreeable  to  the  taste  when  properly  made,  fresh,  and  cold.  It 
loses  its  agreeable  taste  entirely  when  kept  in  a  warm  place,  when 
kept  too  long,  or  when  taken  without  first  being  properly  cooled 
on  ice  or  otherwise. 

Magnesium  oxide  may  be  employed  instead  of  magnesium  car- 
bonate, using  only  five  twelfths  as  much  of  the  oxide.  But  the 
carbonate  is  more  reliable. 


MAGNESIUM   LACTATE. 

MAGNESII   LACTAS. 

Mg(C3H503)d-aq. 

Magnesium  carbonate    ................     I  part 

Lactic  acid   ..........................     2  parts 

Distilled  water  .......................   20  parts 

Dissolve  the  lactic  acid  in  the  water,  add  the  magnesium  car- 
bonate gradually  to  the  solution  gently  heated  in  a  porcelain  dish 
over  a  water-bath.  When  all  the  magnesium  carbonate  has  been 
added  and  dissolved,  filter  the  solution  and  evaporate  it  to  crystal- 
lization. 

Description.  —  A  white,  crystalline,  odorless,  feebly  bitter  salt; 
soluble  in  26  parts  of  water. 

MAGNESIUM  OXIDE. 

MAGNESIA;  u.  s.    LIGHT  MAGNESIA.    LIGHT  MAGNESIUM  OXIDE. 
(Calcined  Magnesia.) 


Light  magnesium  carbonate. 

Rub  it  through  a  No.  60  sieve.  Heat  it  in  a  capacious  unglazed 
earthenware  dish,  with  constant  stirring,  on  a  sand-bath,  until  a 
sample  removed  from  the  center,  cooled,  mixed  with  a  little  water, 


478  MAGNESIUM    OXIDE. 

and  then  dropped  into  diluted  sulphuric  acid,  gives  but  a  very 
slight  effervescence. 

Reaction.  (MgCO3)4.Mg(OH)2.(H2O)5  when  strongly  heated 
is  decomposed  into  5MgO+6H.,O+4CO2. 

Notes.  The  magnesium  carbonate  being  very  light  a  great  deal 
of  it  rises  from  the  dish  like  dust  and  is  scattered  about. 

In  operating  upon  larger  quantities  a  bright,  clean  iron  pot 
may  be  used,  placed  immediately  over  the  fire  and  heated  gradually 
to  dull  redness. 

If  heated  too  strongly  or  too  long  the  magnesia  becomes  "dead- 
burnt"  so  that  it  does  not  become  "hydrated"  and  form  a  gelat- 
inous mass  of  hydroxide  when  mixed  with  water.  This  failure  of 
the  oxide  to  react  with  water  results  whenever  the  carbonate  is 
heated  until  all  of  it  is  completely  decomposed  so  that  no  efferves- 
cence whatever  occurs  when  the  product  is  tested  with  diluted 
sulphuric  acid.  On  the  other  hand,  the  product  may,  if  not  heated 
long  enough,  contain  "much  basic  anhydrous  carbonate  although 
it  gelatinizes  with  water;  in  such  a  case  it  does  not  retain  the 
property  of  becoming  converted  into  gelatinous  hydroxide.  A 
slight  effervescence  with  diluted  sulphuric  acid  is,  therefore,  allow- 
able ;  but  considerable  effervescence  with  diluted  acid  should  con- 
demn the  product. 

Magnesium  oxide  may  also  be  made  in  a  crucible,  packed  nearly 
full  of  magnesium  carbonate  with  the  aid  of  a  pestle,  the  crucible 
being  covered  and  heated  in  an  oven  or  furnace,  first  moderately 
and  finally  to  dull  redness  for  about  an  hour,  after  which  the  con- 
tents may  be  tested,  and  then  heated  again  if  necessary.  But  this 
procedure  is  more  risky,  as  the  product  is  very  liable  to  become 
"dead-burnt"  in  this  way,  since  it  can  not  be  so  frequently  tested 
to  prevent  it. 

Magnesia  must  be  kept  in  small,  filled,  tightly-corked  bottles, 
the  corks  dipped  in  melted  paraffin  to  effectively  exclude  air  so  as 
to  prevent  the  absorption  of  CO2  and  the  consequent  formation  of 
carbonate.  Containers  capable  of  holding  about  50  Gm  of  mag- 
nesia are  perhaps  the  most  suitable  in  size. 

Test.  When  I  Gm  of  magnesia  ("light  magnesia")  is  thor- 
oughly stirred  with  15  ml  of  water  in  a  beaker  and  the  mixture 
allowed  to  stand  in  the  beaker  for  an  hour,  a  semi-translucent 


MAGNESIUM    OXIDE. 


479 


gelatinous  mass  of  magnesium  hydroxide  should  be  formed,  which 
is  firm  enough  to  remain  in  the  beaker  when  the  latter  is  inverted. 
A  magnesia  which  does  not  possess  the  quality  to  thus  form 
hydroxide  is  not  to  be  used  medicinally,  being  inferior. 

Description. — A  white,  very  light  and  extremely  fine  powder; 
odorless  and  tasteless,  but  producing  in  the  mouth  the  sensation 
usually  produced  by  dry,  absorbent,  tasteless,  earthy  substances. 
Insoluble  in  alcohol,  and  practically  insoluble  in  water,  although 
when  moistened  it  exhibits  a  slightly  alkaline  reaction  on  litmus 
paper. 

"Light  magnesia"  is  about  three  times  as  bulky,  weight  for 
weight,  as  "heavy  magnesia." 

Heavy  Magnesia. 

MAGNESIA    PONDEROSA. 

(Heavy  Magnesium  Oxide.) 
MgO=4O.2. 

A  white,  very  fine  powder,  about  three  times  as  dense  as  the 
light  magnesia,  but  otherwise  of  similar  physical  properties.  It 
also  conforms  to  the  reactions  and  tests  given  by  the  Pharmaco- 
poeia for  "Magnesia,"  but  does  not  form  a  gelatinous  hydroxide 
with  water,  or  does  so  only  with  great  difficulty. 

MAGNESIUM   SALICYLATE. 

MAGNESII    SALICYLAS. 

Mg(C7H503)2.4H20=37o.2. 

Salicylic  acid   14  parts 

Distilled  water 200  parts 

Magnesium  carbonate,  sufficient. 

Mix  the  salicylic  acid  and  distilled  water  in  a  large  porcelain 
dish  and  heat  the  mixture  over  a  water-bath.  Add  5  parts  of 
magnesium  carbonate  to  the  hot  liquid,  stir  well,  and  continue 
heating  until  effervescence  ceases. 

Test  a  filtered  portion  of  the  liquid  on  litmus  paper,  and  if  the 


480      .  MAGNESIUM    SALICYLATE. 

reaction  is  acid  add  more  magnesium  carbonate,  enough  to  render 
the  reaction  of  the  liquid  almost  entirely  neutral. 

When  the  liquid  shall  be  almost  or  quite  neutral  to  test-paper, 
let  it  cool,  filter,  and  then  add  enough  salicylic  acid  to  render  the 
reaction  distinctly  acid. 

Filter  again,  and  evaporate  to  crystallization. 

Notes.  In  order  to  obtain  a  product  which  will  keep  well  and 
produce  a  clear  solution  with  water,  it  is  necessary  to  render  the 
liquid  acid  from  an  excess  of  salicylic  acid  before  evaporating  to 
crystallization. 

The  magnesium  carbonate  employed  should  be  free  from  iron  in 
order  to  insure  a  perfectly  colorless  product. 

As  a  supersaturated  solution  may  be  easily  formed  it  is  neces- 
sary to  determine  the  right  degree  of  concentration  of  the  liquid 
by  repeated  trials  during  the  process  of  evaporation. 

The  fine  crystalline  powder  deposited  while  the  liquid  is  stirred 
during  the  process  of  cooling,  is  to  be  collected,  the  crystals  care- 
fully freed  from  adhering  mother-liquor,  and  dried. 

Additional  crops  of  crystals  may  be  obtained  by  evaporation  of 
the  mother-liquor,  but  the  crystals  thus  obtained  are  usually  more 
or  less  colored  (reddish). 

Description. — Colorless  crystals,  permanent  in  the  air,  odorless, 
of  sweetish-bitterish  taste.  Soluble  in  10  parts  of  water,  forming 
a  clear  solution  which  has  a  distinctly  acid  reaction.  Soluble  in 
alcohol. 

MAGNESIUM   SULPHATE. 

MAGNESII     SULPHAS. 

(Epsom  Salt.) 
MgH2SO5.6H2O=246.2. 

Magnesite,  in  powder 20  parts 

Sulphuric  acid  (92.5%  of  H2SO4) 25  parts 

Water    70  parts 

Mix  the  magnesite  in  a  porcelain  dish  with  40  parts 
of  water.  Then  add  about  2  parts  of  the  sulphuric 
acid,  and  stir.  When  effervescence  has  ceased  add  another 


MAGNESIUM    SULPHATE.  .     481 

portion  of  the  acid,  and  again  wait  until  the  reaction  has  subsided. 
Continue  adding  sulphuric  acid  in  portions  in  the  same  manner 
until  about  two-thirds  of  it  has  been  used.  Then  add  about  20 
parts  of  water,  and  heat  the  mixture  to  about  90°.  Add  the  re- 
mainder of  the  acid,  in  portions,  as  before;  then  add  the  rest  of 
the  water,  and  heat  the  whole  at  about  90°  for  two  hours,  stirring 
frequently.  Add  enough  magnesium  carbonate  to  render  the  solu- 
tion neutral  to  litmus  paper.  Set  the  liquid  aside  to  cool  and 
settle.  Filter.  Evaporate  the  filtrate  until  it  has  about  1.33  sp.  w. 
while  still  hot,  and  then  set  it  aside  to  crystallize.  Drain  the  crys- 
tals and  dry  them  at  about  25°. 

Reaction.     MgCO3+H2SO4=MgSO4+H2O4-CO». 

Description. — Small,  colorless,  acicular  crystals  ;  odorless ;  taste 
cooling,  saline,  bitter.  Slightly  efflorescent  in  dry  air.  Soluble  in 
1.5  parts  of  water  at  15°  and  in  0.7  part  of  boiling  water.  Insoluble 
in  alcohol. 

Purified   Magnesium    Sulphate. 

Dissolve  any  desired  quantity  of  commercial  Epsom  salt  in  one 
and  one-half  times  its  weight  of  water,  filter  the  solution  and  set 
it  aside  to  crystallize. 

Should  the  Epsom  salt  contain  iron  the  solution  should  be  di- 
gested with  a  little  magnesium  carbonate  before  crystallization. 
Large  crystals  are  readily  obtained  if  the  crystallization  is  slow. 

Dried  Magnesium  Sulphate. 

MAGNESII    SULPHAS    EXSICCATUS. 

MgH2SO5.H2O=i56.2. 

Expose  crystallized  magnesium  sulphate  in  a  porcelain  dish  to 
the  heat  of  the  water-bath  until  the  salt  ceases  to  lose  weight. 

Notes.  Crystallized  magnesium  sulphate  effloresces  somewhat 
in  dry  air  and  at  from  30°  to  52°  loses  one  molecule  of  water. 
The  dried  salt,  on  the  other  hand,  absorbs  water  from  a  moist  air. 
The  product  must,  therefore,  be  kept  in  tightly  closed  bottles. 

Vol.    II— 31 


482  MAGNESIUM    SULPHITE. 

MAGNESIUM    SULPHITE. 

MAGNESII    SULPHIS. 
MgSO:;.6H2.O=2I2.2. 

By  saturating  either  magnesium  carbonate  or  magnesium  oxide, 
suspended  in  water,  with  sulphurous  oxide,  the  crystalline  product 
being  drained  and  dried. 

Description. — A  white,  crystalline  powder ;  odorless ;  taste  bit- 
terish, somewhat  sulphurous.  Soluble  in  20  parts  of  water. 

Must  be  kept  in  tightly-stoppered  bottles,  as  it  oxidizes  on  ex- 
posure to  air. 

MAGNESIUM  TARTRATE. 

MAGNESII     TARTRAS. 

MgC4H400=i72.2. 

Tartaric  acid   10  parts 

Magnesium   carbonate    6  parts 

Dissolve  the  acid  in  20  parts  of  distilled  water,  keep  the  solution 
hot  over  a  water-bath,  and  add  gradually  the  magnesium  carbon- 
ate until  a  neutral  salt  is  obtained.  Evaporate  to  dryness,  and 
powder  the  residue. 

Description. — A  white  powder  which  is  practically  insoluble  in 
cold  water. 

MANGANESE   CARBONATE. 

MANGANI     CARBONAS. 

MnCO3=ii5. 

Manganous  sulphate 22  parts 

Sodium  bicarbonate    17  parts 

Dissolve  the  bicarbonate  in  200  parts  of  boiling  water ;  add  the 


MANGANESE   DIOXIDE.  483 

sulphate  previously  dissolved  in  100  parts  of  boiling  water  and 
sweetened  with  5  parts  of  sugar.  Wash  the  precipitate  with  boil- 
ing water  containing  about  4  per  cent  of  sugar.  When  the  wash- 
ings give  but  a  slight  turbidity  with  test  solution  of  barium 
chloride,  press  the  water  out  of  the  magma,  and  dry  it  as  rapidly 
as  practicable,  with  the  aid  of  moderate  heat. 

Description. — A  dirty  white  powder  with  a  reddish  tinge.    It  is 
insoluble  in  water,  but  dissolves  in  dilute  acids. 


MANGANESE   DIOXIDE. 

MANGANI   DIOXIDUM. 

(Black  Oxide  of  Manganese.) 


Pure  manganese  dioxide  is  not  obtainable.  The  best  grades  of 
pyrolusite  or  brownstone  contain  about  90  per  cent  of  MnO2.  The 
impurities  in  native  black  oxide  of  manganese  are  ferric  oxide, 
silica,  barium  carbonate,  calcium  carbonate,  alumina,  etc.  The 
American  Pharmacopoeia  requires  the  manganese  dioxide  to  con- 
tain not  less  than  66  per  cent  of  MnO2.  Since  this  is  the  case 
the  official  title  should  not  be  "manganese  dioxide,"  but  "native 
black  oxide  of  manganese." 

In  the  employment  of  the  native  mineral  its  variable  composi- 
tion must  be  taken  into  account.  In  the  trade  the  pyrolusite 
occurs  both  whole  and  powdered.  The  whole  mineral  can  not 
be  adulterated  ;  but  the  powdered  is  frequently  mixed  with  coal, 
etc. 

Extremely  fine  powder  is  necessary  for  some  purposes  ;  but  for 
the  preparation  of  chlorine  from  hydrochloric  acid  a  coarsely 
powdered  or  crushed  pyrolusite  is  the  best. 

The  Pharmacopoeia  describes  it  as  a  heavy,  grayish-black,  more 
or  less  gritty  powder,  without  odor  or  taste.  Insoluble  in  water, 
alcohol,  or  any  other  simple  solvent.  Not  affected  by  cold  sul- 
phuric or  hydrochloric  acid. 


484  MANGANESE    CHLORIDE 

MANGANESE    CHLORIDE. 

MANGANI    CHLORIDUM. 


The  acid  liquid  containing  manganese  chloride  which  remains 
in  the  flask  or  other  generator  when  chlorine  gas  is  prepared  from 
hydrochloric  acid  and  manganese  dioxide  can  be  used  to  make 
manganous  chloride  as  follows  : 

Evaporate  the  liquid  to  dryness  and  continue  the  heat  as  long  as 
acid  vapors  pass  off.  Boil  the  residue  with  water  for  about  ten 
minutes.  Filter  the  solution.  Precipitate  manganous  carbonate 
from  about  one-eighth  of  the  filtrate  with  an  excess  of  sodium 
carbonate  solution;  wash  the  precipitate  and  then  add  it  to  the 
other  seven-eighths  of  the  'filtrate.  Boil  for  about  half  an  hour, 
adding  more  water  if  required.  Filter,  evaporate,  and  crystallize. 

The  preparation  may  be  readily  made  from  manganous  sulphate 
and  barium  chloride. 

Description.  —  Pale  red,  deliquescent  crystals,  soluble  in  alcohol 
as  well  as  water. 


MANGANESE   IODIDE    SYRUP. 

SYRUPUS    MANGANI    IODIDI. 

Manganous  sulphate  ...................     40  Gm 

Potassium  iodide  .  .  ....................     50  Gm 

Sugar    .......................  .  .......   280  Gm 

Simple  syrup,  distilled  water,  each  sufficient. 

Dissolve  each  of  the  salts  in  50  ml  of  water  mixed  with 
jo  ml  of  simple  syrup.  Mix  the  solutions  and  shake  well.  Cool 
the  mixture  to  about  10°  C.  (50°  F.).  Filter,  rinsing  the  pre- 
cipitate on  the  filter  with  a  little  sweetened  water,  letting  the 
filtrate  and  washings  run  into  a  bottle  containing  the  sugar. 
Shake  until  dissolved,  and  then  add  enough  distilled  water  to 
make  the  total  product  measure  400  milliliters. 

Must  be  protected  from  light. 


MANGANESE   IODIDE.  485 

Reaction.     MnSO4+2KI==K2SO4+MnI2. 

Notes.  The  manganous  iodide  is  very  deliquescent  and  prone 
to  rapid  decomposition.  Hence  it  is  not  used  except  preserved 
by  sugar  in  the  form  of  syrup. 

The  application  of  cold  in  the  process  is  to  cause  the  separation 
of  the  potassium  sulphate  as  far  as  possible. 

Description. — A  clear,  pale,  rose-colored  or  pinkish  syrup.  It 
becomes  nearly  colorless  on  standing  if  exposed  to  light,  the  sugar 
becoming  partially  inverted  at  the  same  time. 

MANGANESE    PHOSPHATE. 

MANGANI    PHOSPHAS. 

Mn3(P04)2.4H20=427. 

Manganous   sulphate 10  parts 

Sodium  phosphate 1 1  parts 

Dissolve  the  salts,  separately,  each  in  80  parts  of  hot  water, 
filter,  and  let  the  solutions  cool.  Mix  them.  Wash  the  precipi- 
tate with  water  until  the  washings  cease  to  give  any  reaction  for 
sulphate.  Dry  the  product  with  the  aid  of  gentle  heat,  avoiding 
unnecessary  exposure  to  the  air. 

Reaction. 

3  ( MnSO4.4H2O )  +2  ( Na2HPO4. 1 2H2O) 

=Mn3(PO4)2.4H1)O+2(Na,SO4.ioH2O)+H2SO4+i2H2O. 

Notes.  As  will  be  seen,  the  reaction  is  analogous  to  that  oc- 
curring in  the  preparation  of  ferroso-ferric  phosphate.  Loss  of 
product  is  sustained  by  reason  of  the  solubility  of  manganous 
phosphate  in  the  sulphuric  acid  formed.  The  free  acid  may  be 
carefully  neutralized  by  the  addition  of  sodium  bicarbonate  to 
obviate  this  loss. 

Description. — An  almost  white  (slightly  pinkish)  powder,  odor- 
less and  tasteless ;  insoluble  in  water  and  in  alcohol. 


486  MANGANESE    SULPHATE. 

MANGANOUS    SULPHATE. 

MANGANI    SULPHAS. 


Manganese  dioxide. 
Concentrated  sulphuric  acid. 
Sodium  carbonate. 
Water. 

Mix  the  finely  powdered  manganese  dioxide  with  a  sufficient 
quantity  of  strong  sulphuric  acid  to  form  a  very  soft  paste.  Heat 
this  mixture  in  a  porcelain  dish,  strongly,  on  a  sand-bath,  stir- 
ring constantly,  until  dry.  Then  transfer  the  dry  mass  to  a 
Battersea  crucible  and  keep  it  at  a  red  heat  for  about  an  hour. 
Let  cool.  Leech  out  the  salt  with  hot  water,  filter  the  solution. 

Set  aside  seven-eighths  of  this  solution.  To  the  remaining 
eighth  add  a  solution  of  sodium  carbonate  (  i  part  of  carbonate  in 
10  parts  of  water)  as  long  as  a  precipitate  falls.  Wash  this  pre- 
cipitated manganous  carbonate  by  decantation  until  the  washings 
are  free  from  sulphate. 

Then  add  the  washed  magma  of  manganous  carbonate  to  the 
reserved  portion  of  the  solution  of  manganous  sulphate,  mix 
well,  and  heat  the  mixture  in  a  porcelain  dish  to  boiling. 

Filter,  and  evaporate  the  filtrate  to  crystallization. 

Collect,  drain,  and  dry  the  crystals. 

Bottle  the  product  at  once  as  soon  as  the  crystals  are  dry  to 
the  touch. 

Reaction.     2MnO2+2H2SO4=2MnSO4+2H2O+O2. 

Notes.  The  solution  of  manganous  sulphate  obtained  from  one 
kilo  of  manganese  dioxide  may  be  evaporated  to  about  90.0 
Cc.  and  then  set  aside  in  a  shallow  dish,  over  sulphuric 
acid,  in  a  desiccator,  when  a  solid  cake  of  crystals  will 
be  obtained  in  a  few  days,  at  the  ordinary  room  tem- 
perature. These  crystals,  however,  contain  5  molecules  of 
water.  The  Pharmacopoeia  orders  a  salt  with  4  molecules  of 
water,  and  this  can  be  obtained  by  redissolving  the  manganous 
sulphate  obtained  as  described  in  an  equal  weight  of  water  and 
letting  this  solution  stand  in  a  dish  at  30°  until  crystallization 


MANGANESE   SULPHATE.  '        487 

takes  place.  At  a  very  low  temperature  the  salt  crystallizes  with 
7  molecules  of  water. 

When  the  crystals  are  drained  they  should  be  covered  with  a 
damp  piece  of  cloth  to  prevent  efflorescence. 

The  object  of  adding  manganous  carbonate  to  the  solution  of 
manganous  sulphate  is  the  precipitation  and  removal  of  any  iron, 
which  may  still  remain  after  the  ignition  which  decomposes  nearly 
all  of  the  iron  sulphate  without  decomposing  the  manganese  salt. 

Description. — Pale  rose-colored,  or  colorless;  transparent  crys- 
tals ;  odorless ;  taste  slightly  bitter,  astringent.  Efflorescent  in  dry 
air.  Soluble  in  0.8  part  of  water  at  15°,  and  in  I  part  of  boiling 
water.  Insoluble  in  alcohol. 


MERCURY;    PURIFIED. 

HYDRARGYRUM    PURIFICATUM. 
Hg3=2OO. 

Mercury    10  parts 

Nitric  acid. I  part 

Water    5  parts 

Put  the  metal  with  the  acid  and  water  in  a  porcelain  dish  and 
let  them  remain  together  during  four  days,  stirring  the  contents 
frequently  and  strongly.  Then  pour  off  the  acid  liquid,  and  wash 
the  metal,  first  with  water  and  finally  with  distilled  water,  until 
the  washings  no  longer  give  an  acid  reaction  on  litmus  paper. 
Dry  the  mercury  by  pouring  it  through  a  cone  made  of  white 
filter  paper  or  blotting  paper  and  having  an  aperture  at  the  apex 
barely  large  enough  to  admit  a  pin,  so  that  the  metal  passes 
through  in  a  thin  stream. 

Notes.  Common  mercury  usually  contains  one  or  more  of  the 
metals,  lead,  tin,  copper,  antimony,  arsenic,  bismuth.  Such  impure 
mercury  sometimes  presents  a  dull  surface.  Drops  of  mercury 
containing  lead  do  not  retain  their  globular  form  when  made 
to  roll  about  on  white  paper,  but  leave  streaks  or  traces  and  may 
even  form  little  tail-like  projections. 

Nitric  acid  attacks  the  tin,  antimony  and  some  of  the  other 
metals  before  it  attacks  the  mercury  and  removes  them,  leaving 


488  PURIFIED    MERCURY. 

the  mercury  purer  than  before,  and  sufficiently  pure  for  the  prep- 
aration of  the  mercury  compounds  to  be  employed  for  pharma- 
ceutical purposes. 

Mercury  boils  at  357. °25  C.  (U.  S.  P.),  and  the  most  effective 
method  of  purification  of  commercial  mercury  is  distillation. 

Mercury  should  present  a  perfectly  bright  surface,  but  it  may 
present  a  dark  colored  film  or  patches  on  the  surface  if  contam- 
inated with  dust,  dirt,  moisture,  or  the  oxides  of  the  foreign 
metals  present.  To  restore  its  brightness  it  is  only  necessary 
to  run  the  metal  through  a  paper  cone  as  before  described ;  but 
if  other  metals  are  present  the  mercury  becomes  dull  and  dirty 
again  from  metallic  oxides  floating  on  its  surface. 


MERCURIC    BENZOATE. 

HYDRARGYRI    BENZOAS. 

Hg(C6HBC02)2=442. 

Freshly  precipitated  mercuric  oxide  from  27  parts -of  mercuric 
chloride  is  mixed  with  22.5  parts  of  artificial  benzoic  acid  (from 
toluol)  and  the  mixture  digested  at  a  temperature  near  the  boil- 
ing point  (at  full  water-bath  heat)  until  the  yellow  color  of  the 
mercuric  oxide  has  given  place  to  the  yellowish-white  color  of 
the  mercuric  benzoate  formed.  The  product  forms  voluminous 
masses  floating  in  the  liquid. 

Let  the  liquid  cool  to  50°  C.,  transfer  the  whole  mixture  to  a 
cloth  strainer  or  a  paper  filter,  according  to  the  quantity  operated 
upon,  and  wash  the  benzoate  with  water  of  the  temperature  of 
from  50°  to  60°  C. 

Dissolve  the  salt  in  boiling  water  and  let  the  solution  cool  so 
that  the  product  may  be  obtained  in  crystals.  Dry  these  at  from 
40°  to  50°  C. 

Description. — Mercuric  benzoate  thus  prepared  is  in  colorless, 
glistening  crystal  needles,  of  a  somewhat  metallic  taste.  Gives  an 
acid  reaction  on  moist  blue  litmus  paper.  Nearly  insoluble  in 
cold  water,  but  freely  soluble  in  boiling  water.  Readily  soluble 
in  a  water  solution  of  sodium  chloride,  and  this  solution  has  been 
used  for  hypodermatic  injection.  Soluble  in  alcohol  but  with 
partial  decomposition.  It  contains  about  45.2  per  cent  of  Hg. 


MERCURIC   BROMIDE.  489 

MERCURIC    BROMIDE. 

HYDRARGYRI    BROMIDUM. 

HgBr,=36o. 

Mercury 5  parts 

Bromine 4  parts 

Water 25  pans 

Place  the  metal  in  a  flask;  add  the  water;  then  the  bromine. 
Apply  heat,  gradually  increased,  until  the  mercury  is  dissolved. 
Boil,  filter,  and  then  crystallize. 

Reaction.     Hg4-2Bn=HgBr2. 

Notes.  The  action  is  at  first  slow,  but  when  some  HgBr2  has 
been  formed  the  bromine  dissolves  more  freely  and  the  reaction 
goes  on  rapidly. 

If  necessary,  a  little  more  bromine  should  be  added  to  com- 
plete the  solution  of  the  last  of  the  mercury. 

Description. — A  white,  odorless,  crystalline  solid ;  soluble  in 
20  parts  of  water  at  15°. 

MERCURIC    CHLORIDE. 

HYDRARGYRI    CHLORIDUM    CORROSIVUM. 

(Corrosive  Sublimate.      Corrosive  Chloride  of  Mercury.) 
HgCl2=27o.8. 

Mercuric  sulphate 20  parts 

Sodium  chloride 15  parts 

Manganese   dioxide I  part 

Mix  the  dried  and  powdered  materials  and  triturate  the  mix- 
ture thoroughly  until  a  uniform  and  very  fine  powder  is  obtained. 
Put  this  into  a  suitable  vessel  and  heat  in  a  sand-bath  until  the 
mercuric  chloride  has  been  sublimed. 

Reaction.     HgSO4+2NaCl=Na2SO4+HgCl2. 


490  MERCURIC    CHLORIDE. 

Notes.  The  materials  must  be  thoroughly  dry  and  reduced  to 
very  fine  powder.  The  manganese  dioxide  should  be  strongly 
heated  after  having  been  powdered  and  before  it  is  mixed  with 
the  other  substances. 

•On  a  small  scale  the  same  apparatus  as  described  in  the  notes 
under  the  head  of  Hydrargyri  Chloridum  Mite  may  be  employed. 
Or  a  retort  may  be  used  having  the  neck  cut  off  rather  short  so 
as  to  leave  a  wide  opening.  The  retort  should  be  buried  in  the  dry 
sand  up  to  the  neck.  Heat  is  then  applied  gradually.  If  the  ma- 
terials were  not  perfectly  dry  water  vapor  will  be  formed,  and  it  is 
then  necessary  to  heat  gently  at  first  until  the  moisture  shall  have 
been  expelled,  and  even  the  neck  of  the  retort  should  be  warmed 
sufficiently  to  insure  the  expulsion  of  all  water  vapor.  The  iron 
dish  employed  for  the  sand-bath  is  then  heated  more  and  more 
strongly  until  sublimation  is  effected,  the  end  of  the  neck  of 
the  retort  being  capped  with  a  wide-mouthed  bottle.  The  heat  is 
continued  until  the  sublimation  is  completed,  care  being  taken 
not  to  permit  the  neck  of  the  retort  to  become  choked  up.  To- 
wards the  close  of  the  process  the  heat  is  raised  almost  to  the 
fusing  point  of  the  mercuric  chloride  in  order  to  obtain  a  sub- 
limate of  more  decidedly  developed  crystalline  structure.  The 
retort  is  finally  allowed  to  cool  slowly,  after  which  the  sublimate 
may  be  readily  removed  from  the  short  neck. 

In  order  to  obviate  the  danger  of  inhaling  any  vapor  of  mer- 
curic chloride  it  is  necessary  that  the  whole  operation  be  carried 
out  in  a  hood  with  a  good  draught.  The  product  must  not  be 
carelessly  handled,  being  extremely  poisonous.  If  it.  is  desired 
to  powder  corrosive  sublimate,  it  should  be  kept  dampened  with 
alcohol  during  the  process  of  trituration,  to  prevent  the  rising  of 
dust. 

Should  the  mercuric  sulphate  employed  contain  any  mercurous 
sulphate  a  corresponding  quantity  of  mercurous  chloride  must 
be  produced.  To  prevent  this  the  manganese  dioxide  is  added. 
The  rationale  of  its  action  is  shown  in  the  following  equation : 

Hg2SO4+MnO2+2NaCl=Na2SO4+2HgO+MnCl2. 

Without  the  addition  of  manganese  dioxide  it  is  scarcely  pos- 
sible to  obtain  a  corrosive  sublimate  that  does  not  contain  calomel 


MERCURIC   CHLOPIDE. 

to  such  an  extent  as  to  produce  a  very  unclear  solution  in  water. 
But  the  sublimed  mercuric  chloride  may  be  dissolved  in  diluted 
alcohol  and  crystallized  from  the  filtered  solution. 

Another  Method. 

Mercuric   oxide 9  parts 

Hydrochloric  acid  (32%  of  HC1) 10  parts 

Distilled  water 500  parts 

Heat  together  until  the  oxide  is  completely  dissolved.  Filter 
the  hot  solution,  and  evaporate  it  to  dryness.  Crystallize  the 
product. 

Reaction.     HgO+2HCl=rHgCl2+H2O. 

Notes.  The  product  obtained  by  this  method  may  be  sublimed 
to  obtain  it  in  the  form  of  crystals  or  crystalline  masses,  or  it 
may  be  crystallized  in  needles  from  a  solution  made  with  warm 
diluted  alcohol,  or  with  water. 

Solutions  of  mercuric  chloride  for  certain  purposes  may  be 
readily  made  of  definite  strength  from  mercuric  oxide,  hydro- 
chloric acid  and  water  in  such  proportions  as  may  be  required. 
The  hydrochloric  acid  is  prescribed  in  slight  excess. 

Description. — Heavy,  transparent,  colorless,  odorless  crystals  or 
crystalline  masses,  having  an  acrid,  nauseous,  persistent,  metallic 
taste.  It  is  extremely  poisonous,  and  should,  therefore,  not  be 
tasted  except  in  the  most  cautious  manner. 

Obtained  by  sublimation  on  a  large  scale,  or  heated  at  or  near 
its  fusing  point  (about  265°)  and  then  very  slowly  cooled,  it 
forms  large,  transparent,  colorless  crystals.  When  crystallized 
from  solutions  it  is  obtained  in  the  form  of  long  needles  which 
are  somewhat  opaque.  Soluble  in  16  parts  of  water,  and  in 
3  parts  of  alcohol,  at  15°  ;  in  2  parts  of  boiling  water,  and  in  1.2 
parts  of  boiling  alcohol ;  also  in  4  parts  of  ether,  and  in  14  parts 
of  glycerin. 

Mercuric  chloride  dissolves  so  slowly  in  water  that  in  making 
solutions  of  it  the  most  advantageous  procedure  is  to  employ 
.powdered  chloride  and  hot  water. 


492  MERCURIC    CHLORAMIDE. 

MERCURIC    CHLORAMIDE. 

HYDRARGYRUM    AMMONIATUM. 

( Mercurammonium    Chloride.      Ammoniated    Mercury.     White 

Precipitate.) 

H2NHgCl=25i.4. 

Mercuric   chloride 10  parts 

Ammonia  water,  distilled  water,  each  sufficient. 

Dissolve  the  chloride  in  200  parts  of  warm  distilled  water; 
filter  and  allow  to  cool.  Pour  the  filtrate  gradually  and  during 
constant  stirring  into  5  parts  of  ammonia  water,  taking  care  that 
the  ammonia  shall  remain  in  excess  when  all  of  the  mercuric 
chloride  has  been  added.  Collect  the  precipitate  at  once  on  a  filter, 
drain  as  much  as  possible,  and  then  wash  it  twice,  each  time 
with  a  mixture  of  20  parts  of  distilled  water  and  I  part 
of  ammonia  water.  Finally,  dry  the  precipitate  between  filter 
paper  in  a  dark  place  at  a  temperature  not  exceeding  30°  C. 
(86°  R). 

Reaction.     HgCl2+2H4NOH=H4NCl+H2NHgCl+2H2O. 

Notes,  When  a  solution  of  mercuric  chloride  is  poured  into 
ammonia  water,  the  latter  being  in  excess  throughout,  the  official 
ammoniated  mercury  is  formed. 

When,  however,  the  order  of  mixing  the  liquids  is  reversed, 
the  ammonia  water  being  added  to  the  mercuric  chloride,  or  when 
the  mercuric  chloride  is  present  in  excess  over  the  propor- 
tion of  ammonia  used,  the  product  will  be,  or  will  contain, 
H2N(HgCl)2Cl  instead  of  H2NHgCl.  The  H2N(HgCl)2Cl  is, 
however,  converted  into  the  official  mercurammonium  chloride 
when  allowed  to  remain  in  contact  with  an  excess  of  ammonia  for 
some  time. 

Some  pharmacopoeias  order  the  addition  of  the  ammonia  to 
the  solution  of  mercuric  chloride;  others,  including  ours,  direct 
the  opposite  order  of  mixing. 

Mercurammonium  chloride  is  perfectly  white.  A  grayish 
color  indicates  that  the  solution  of  mercuric  chloride  was  not 
filtered  before  adding  it  to  the  ammonia,  whereby  the  calomel, 


MERCURIC    CHLORAMIDE.  493 

which  is  always  present  in  corrosive  sublimate,  gives  rise  to  mer- 
curous  oxide.  If  warm  liquids  are  used,  or  if  the  precipitate  be 
washed  with  warm  water  or  too  long,  or  if  ammonia  is  not  pres- 
ent in  the  washing  and  drying,  the  product  will  be  more 
or  less  yellow  from  hydroxyl-dimercurammonium  chloride 
(HNOHHg2Cl).  The  same  result  follows  if  a  too  high  tem- 
perature is  used  in  drying.  Exposure  to  light  renders  it  grayish. 

The  preparation  must  be  kept  in  well  closed  bottles,  in  a  cool 
place,  and  protected  from  light. 


MERCURIC    CYANIDE. 

HYDRARGYRI    CYANIDUM. 

Hg(CN)2=252. 

Potassium   f errocyanide 60  parts 

Solution  of  ferric  chloride  (U.  S.) 83  parts 

Mercuric  oxide. 
Water. 

Dissolve  the  potassium  ferrocyanide  in  600  parts  of  hot  water, 
and  filter.  Dilute  the  solution  of  ferric  chloride  with  750  parts 
of  water.  Pour  the  solution  of  potassium  ferrocyanide  gradually 
into  the  solution  of  ferric  chloride,  stirring  constantly.  Set  the 
mixture  aside  until  the  precipitate  has  subsided  as  far  as  it  may. 
Decant  the  supernatant  liquid.  Add  to  the  magma  about  1,000 
parts  of  boiling  water  acidulated  with  10  parts  of  hydrochloric 
acid,  stir  well,  and  let  the  mixture  stand  until  the  ferrocyanide 
of  iron  has  again  settled.  Decant,  and  add  another  1,000  parts 
of  boiling  water,  acidulated  as  before ;  mix  thoroughly ;  let  settle, 
and  decant  again.  Repeat  the  washing  of  the  precipitate  at  least 
twice  again  in  the  same  manner.  Then  mix  the  blue  magma 
well  with  1,000  parts  of  boiling  water  (this  time  not  acidulated), 
let  settle,  and  decant.  Transfer  the  wet  mass  to  a  muslin  strainer 
and  continue  the  washing  with  pure  boiling  water  until  the  wash- 
ings are  no  longer  rendered  turbid  by  test-solution  of  silver 
nitrate.  When  the  washing  has  been  completed  enclose  the 
magma  in  the  strainer  and  express  the  water  from  it  as  far  as 
possible.  Dry  the  iron  ferrocyanide  in  a  porcelain  dish  with 
the  aid  of  moderate  heat. 


494  MERCURIC    CYANIDE. 

Triturate  I  part  of  this  ferrocyanide  of  iron  with  2  parts  of 
mercuric  oxide  until  thoroughly  mixed.  Put  the  mixture  in  a 
porcelain  dish,  add  20  parts  of  water,  and  heat  upon  a  water-bath 
for  one  hour,  stirring  frequently  and  replacing  the  water  lost  by 
evaporation.  Then  boil  the  mixture  until  the  blue  color  disap- 
pears. Should  a  blue  color  still  remain  after  boiling  the  mix- 
ture for  ten  minutes,  add  a  little  more  mercuric  oxide  and  con- 
tinue boiling  until  the  color  of  the  insoluble  matter  becomes  black. 

Filter  the  liquid.  Boil  the  black  precipitate  with  about  10 
parts  of  water,  filter,  and  add  this  liquid  to  the  other  filtrate. 
Supersaturate  the  united  filtrates  with  hydrocyanic  acid,  using 
enough  to  impart  a  permanent  odor  of  that  acid  to  the  liquid. 

Now  filter  the  solution  and  evaporate  to  crystallization. 

Collect  the  crystals  in  a  funnel,  let  drain,  and  then  dry  them 
on  a  filter  paper  with  the  aid  of  moderate  heat. 

Evaporate  the  mother-liquor  to  obtain  additional  crystals  in 
the  usual  way. 

Reactions. 

First,  3K4Fe(Cy)6+4FeCl3=Fe4(FeCy6)3+i2KCl;  and  then 
Fe4(FeCy6)3+9HgO+9H20 

=9HgCy2+3Fe(OH),4Fe(OH)3. 

Notes.  The  precipitated  iron  ferrocyanide  contains  potassium 
compound  and  the  wash  water  is  acidulated  with  hydrochloric 
acid  to  remove  that  compound.  In  order  to  render  the  precipi- 
tate more  dense,  to  facilitate  the  otherwise  extremely  difficult 
washing,  boiling  water  is  repeatedly  employed.  The  washing  is 
completed  with  pure  water  to  remove  the  hydrochloric  acid  as 
well  as  the  last  traces  of  potassium  chloride.  To  facilitate  the 
drying  of  the  ferrocyanide  the  water  is  forcibly  pressed  out, 
and  the  finely  divided  "prussian  blue"  is  then  spread  out  thinly 
over  the  bottom  and  inner  sides  of  a  large  porcelain  dish  and 
moderate  heat  used. 

To  make  the  mercuric  cyanide  from  ferrocyanide  of  iron,  the 
latter  must  be  recently  precipitated  and  of  the  right  composition. 
Hence  the  commercial  "prussian  blue"  can  not  be  successfully 
employed. 

The  solution  of  mercuric  cyanide  obtained  by  boiling  ferro- 


MERCURIC    CYANIDE. 


495 


cyanide  of  iron  with  mercuric  oxide  contains  some  basic  salt 
("oxy-cyanide  of  mercury"),  and  it  is,  therefore,  necessary  to 
acidulate  this  solution  with  hydrocyanic  acid.  Some  iron  usually 
precipitates  on  this  addition  of  hydrocyanic  acid. 

The  hydrocyanic  acid  required  for  this  purpose  may  be  made 
from  potassium  cyanide.  A  sufficient  quantity  for  the  product 
obtained  from  60  parts  of  potassium  ferrocyanide  will  be  pro- 
duced by  4  parts  of  potassium  cyanide  which  may  be  dissolved  in 
80  parts  of  diluted  alcohol  and  mixed  with  9.2  parts  of  tartaric 
acid  after  which  the  mixture  is  allowed  to  stand  for  one  hour  and 
then  filtered. 

Another  Method. 

Potassium    cyanide 26  parts 

Tartaric   acid 60  parts 

Mercuric   oxide 43  parts 

Diluted  alcohol 500  parts 

Water. 

Dissolve  the  potassium  cyanide  in  the  diluted  alcohol.  Add 
the  powdered  tartaric  acid  and  shake  well.  Let  the  mixture 
stand  one  hour,  shaking  occasionally.  Filter  in  a  covered  fun- 
nel into  a  bottle.  Add  the  mercuric  oxide  to  the  filtrate  and  let 
stand,  shaking  frequently,  until  the  odor  of  hydrocyanic  acid 
has  nearly  ceased  and  the  mercuric  oxide  has  dissolved.  Evapor- 
ate the  filtered  solution  to  crystallization,  after  first  adding  some 
more  hydrocyanic  acid. 

Reactions. 

First,  KCy+H2C4H406=KHC4H406+HCy;  then 
HgO+2HCy=HgCy2+H2O. 

Notes.  Should  the  solution  of  mercuric  cyanide  be  basic  it 
deposits  mercuric  oxide  on  evaporation.  It  is,  therefore,  neces- 
sary to  have  the  hydrocyanic  acid  in  excess.  It  is  best  to  dissolve 
the  mercuric  oxide  and  then  add  enough  hydrocyanic  acid  to 
impart  its  odor  to  the  liquid.  (See  notes  under  preceding 
formula.) 

Description. — Colorless  or  white  crystals ;  odorless ;  of  bitter 
metallic  taste,  It  is  extremely  poisonous,  and,  therefore,  should 


496  MERCURIC    CYANIDE. 

not  be  tasted  except  in  a  diluted  condition  and  with  the  utmost 
caution. 

It  is  darkened  by  exposure  to  light  and  must,  therefore,  be  kept 
in  dark  amber-colored  bottles  or  in  a  dark  place. 

Soluble  at  15°  in  12.8  parts  of  water,  and  in  15  parts  of  alcohol; 
in  3  parts  of  boiling  water  and  in  6  parts  of  boiling  alcohol. 


MERCURIC    IODIDE. 

HYDRARGYRI    IODIDUM    RUBRUM. 

(Red  Iodide  of  Mercury.) 

HgI2=453- 

Mercury 4  parts 

Iodine 5  parts 

Alcohol. 

Triturate  the  iodine  in  a  glazed  porcelain  mortar  (or  in  a  glass 
mortar)  with  2  parts  of  alcohol.  Add  the  mercury.  Continue 
the  trituration  until  a  uniform  scarlet  red  powder  has  been  ob- 
tained, adding  a  little  more  alcohol  from  time  to  time  as  may 
be  necessary  to  keep  the  mixture  moist  until  the  chemical  reac- 
tion shall  have  been  accomplished  as  tar  as  practicable. 

Reaction.     Hg+  I2=HgI2. 

Notes.  A  pure  mercuric  iodide  is  not  obtained  by  this  method 
for  the  reaction  is  not  complete.  The  alcohol  is  added  to  pre- 
vent the  vaporization  of  any  of  the  iodine  by  the  heat  generated 
by  the  reaction,  the  alcohol  being  evaporated  instead  of  the  iodine 
and  the  temperature  thereby  reduced. 

This  method  is  not  recommended,  but  is  included  in  this  man- 
ual only  as  an  illustration  of  the  preparation  of  chemical  prod- 
ucts by  dry  trituration. 

The  product  obtained  from  4  parts  of  mercury  and  5  parts  of 
iodine  may  be  put  in  a  flask  with  160  parts  of  alcohol  and  dis- 
solved by  boiling;  the  hot  solution  may  then  be  poured  into  a 
beaker  and  allowed  to  cool  slowly  in  order  to  obtain  the  mercuric 
iodide  in  crystals. 

\ 


MERCURIC    IODIDE.  497 

Wet  Process. 

Mercuric  chloride,  in  powder 12  parts 

Potassium   iodide 15  parts 

Dissolve  the  mercuric  chloride  in  200  parts  of  hot  distilled 
water,  and  filter.  Dissolve  the  potassium  iodide  in  40  parts  of 
cold  distilled  water,  and  filter. 

Pour  the  solution  of  mercuric  chloride,  when  cold,  slowly,  into 
the  solution  of  potassium  iodide,  stirring  constantly.  Set  aside 
until  the  precipitate  has  subsided  perfectly.  Decant  the  mother 
liquor  and  reject  it.  Wash  the  precipitate  with  300  parts  of  cold 
water,  stirring  it  up  well,  allowing  it  to  subside  again,  and  at 
once  decanting  the  washings.  Then  collect  the  precipitate  upon  a 
white  paper  filter,  and  continue  washing  with  distilled  water  until 
the  washings  cease  to  give  a  precipitate  with  test-solution  of  silver 
nitrate. 

Dry  the  iodide  between  white  filter  paper  at  a  temperature  not 
exceeding  40°  C.  (104°  F.).  Keep  it  in  well  closed  bottles. 

Reaction.     HgCl2+2KI=HgI2+2KCl. 

Notes.  Theoretically  we  should  require  for  12  parts  of  mer- 
curic chloride  about  14.7  parts  of  potassium  iodide;  but  the  potas- 
sium iodide  generally  contains  small  quantities  of  carbonate  and 
other  impurities,  and  it  is  moreover  desirable  to  use  a  slight  ex- 
cess of  the  potassium  iodide,  to  prevent  the  formation  of  a  light- 
red  compound  of  mercuric  chloride  with  mercuric  iodide.  For 
this  reason,  also,  the  solution  of  mercuric  chloride  must  be  poured 
into  that  of  the  potassium  iodide  so  as  to  keep  the  latter  at  all 
stages  of  the  process  in  excess  over  the  mercuric  chloride  with 
which  it  is  being  mixed,  and  constant  stirring  is  directed  with 
the  same  object  in  view. 

Unless  the  solutions  are  filtered  before  mixing  them,  the  prod- 
uct, besides  retaining  mechanical  impurities,  may  possibly  also 
contain  mercurous  chloride,  the  mercuric  chloride  being  fre- 
quently contaminated  with  calomel. 

Crystallized  mercuric  iodide.  Use  the  same  materials  and  in 
the  same  proportions  as  given  above,  but  use  hot  solutions.  The 
mercuric  iodide  being  soluble  in  a  hot  solution  of  potassium  chlor- 
ide, the  product  crystallizes  in  the  gradual  cooling. 

Vol.  11-32. 


49^  MERCURIC    IODIDE. 

Being  soluble  in  15  parts  of  boiling  alcohol,  the  mercuric  iodide 
may  be  easily  crystallized  from  a  hot  alcoholic  solution. 

Description.  —  A  scarlet-red,  heavy,  odorless  and  tasteless  pow- 
der. Amorphous  if  made  by  triturating  mercury  and  iodine  to- 
gether, or  by  cold  precipitation  ;  crystalline  if  made  by  precipita- 
tion with  hot  solutions.  Brilliant,  although  small,  crystals  can  be 
obtained  from  a  hot  alcoholic  solution. 

Soluble  in  130  parts  of  alcohol  at  15°,  and  in  15  parts  of  boiling 
alcohol.  Soluble  also  in  solutions  of  potassium  iodide,  mercuric 
chloride,  and  sodium  thiosulphate,  respectively. 

Becomes  yellow  when  heated  to  about  150°,  but  turns  scarlet 
again  on  cooling.  It  fuses  at  about  238°  to  a  dark-yellow  liquid 
which  forms  a  mass  of  minute  yellow  crystals  on  cooling,  but 
these  crystals  turn  red  again  after  a  time  (or  at  once,  if  triturated)  . 

MERCURIC    NITRATE    SOLUTION. 

LIQUOR    HYDRARGYRI    NITRATIS. 

A  liquid  containing  about  60  per  cent  of  mercuric  nitrate 
(Hg(NO3)  2=324)  together  with  about  11  per  cent  of  free  nitric 
acid. 

Red  mercuric  oxide  .....................   8  parts 

Nitric   acid  ............................   9  parts 

Distilled  water  .........................   3  parts 

Mix  the  acid  and  water  and  dissolve  the  oxide  in  the  mixture. 
Keep  the  solution  in  glass  stoppered  bottles. 
Reaction.     HgO+2HNO3=Hg  (  NO3  )  2+H2O. 

Description.  —  A  clear,  colorless,  heavy,  corrosive  liquid,  strongly 
acid  in  its  reaction,  and  having  an  odor  of  nitric  acid.  The  sp.  w. 
is  about  2.100  at  15°  C. 

British  Solution  of  Mercuric  Nitrate. 

The  "liquor  hydrargyri  nitratis  acidus"  of  the  British  Pharma- 
copoeia is  prepared  as  follows: 


Mercury   .............................   40° 

Nitric  acid  .......................  .  ----   5°°  ml 

Distilled  water  .....................  ...    150  ml 


MERCURIC    NITRATE.  499 

.  Mix  the  acid  and  water  in  a  flask.  Dissolve  the  mercury  in  the 
mixture  without  the  aid  of  heat.  Then  boil  gently  for  fifteen 
minutes,  or  until  a  drop  of  the  liquid  no  longer  gives  any  pre- 
cipitate in  dilute  hydrochloric  acid.  Let  it  cool,  and  preserve  the 
solution,  which  should  weigh  about  1,200  Gm,  in  a  stoppered  bot- 
tle away  from  the  light. 

Reaction.     3Hg+8HNO8=3Hg(NO,)2+4H2O+2NO. 

Nitrate  of  Mercury  Ointment. 

UNGUENTUM    HYDRARGYRI    NITRATIS. 

(Citrine  Ointment.) 

Mercury 14  parts 

Nitric  acid  (68% ) 35  parts 

Lard  oil 152  parts 

Heat  the  lard  oil  in  a  porcelain  dish  to  a  temperature  of  100°  C. : 
remove  the  dish  from  the  source  of  heat ;  gradually  add  to  the  oil 
14  parts  of  nitric  acid,  and,  when  the  effervescence  caused  by  tlu 
reaction  begins  to  subside,  heat  the  dish"  again  to  60°  until  the 
reaction  is  completed  and  effervescence  has  ceased.  Then  allow 
the  mixture  to  cool  down  to  about  40°  C. 

Dissolve  the  mercury  in  21  parts  of  nitric  acid  with  the  aid  of 
sufficient  heat  to  prevent  the  solution  from  crystallizing,  and  add 
this  liquid  to  the  warm  mixture  made  of  lard  oil  and  nitric  acid 
as  above  described.  Stir  well,  and  then  let  the  mixture  stand 
until  cold,  after  which  it  must  be  again  mixed  thoroughly  in  a . 
porcelain  mortar  or  dish  with  a  pestle  of  the  same  material, 
using  a  spatula  of  horn,  wood,  or  porcelain  to  remove  the  ointment 
from  the  mortar  and  pestle. 

Notes.  The  reactions  occurring  when  fat  is  treated  with  strong 
nitric  acid  are  not  well  known  ;  however,  the  lard  oil  is  acted  upon 
with  more  or  less  energy  according  to  the  temperature,  and  the 
olein  is  converted  by  oxidation  at  the  expense  of  the  nitric  acid 
into  elaidin,  which  is  a  firmer  fat,  having  a  fusing  point  of  about 
32°  C.  It  is  necessary  that  the  nitric  acid  used  should  be  of  full 
strength  in  order  that  this  reaction  may  be  completed  before  the 
solution  of  mercuric  nitrate  is  added.  If  the  temperature  is  per- 
fectly controlled,  the  acid  used  of  full  strength,  and  the  reaction 


5OO  MERCURIC    NITRATE. 

thoroughly  completed  before  the  nitrate  of  mercury  is  added,  the 
product  will  be  a  handsome,  firm,  lemon  yellow  ointment.  If  the 
heat  is  too  high,  the  mercury  nitrate  will  be  decomposed  and  the 
product  rendered  brown,  or  gray  from  mercury  oxide  and  reduced 
metal. 

In  mixing  the  mercuric  nitrate  solution  with  the  oxidized  fat,  it 
is  necessary  to  stir  well  with  a  porcelain  spatula  or  glass  rod 
until  nearly  cold,  in  order  to  thoroughly  incorporate  the  heavy 
liquid  which  might  otherwise  settle  to  the  bottom  of  the  capsule. 

The  solution  of  mercuric  nitrate  to  be  added  to  the  ointment 
may  be  advantageously  made  by  dissolving  mercuric  oxide  (in- 
stead of  the  metal)  in  nitric  acid. 


MERCURIC    OLEATE. 

HYDRARGYRI    OLEAS. 

Hg(C18H3302)2=762. 

Mercuric  oxide 30  Gm 

Nitric  acid  ( 1.42  sp.  gr.) 26  Gm 

Solution  of  potassium  oleate 1,500  ml 

Mix  the  oxide,  the  acid,  and  200  ml  of  distilled  water,  in  a 
beaker  or  an  evaporating  dish,  and  heat  the  mixture  until  the 
oxide  dissolves,  adding  a  few  drops  more  of  nitric  acid,  if  neces- 
sary. Dilute  the  solution  of  mercuric  nitrate  thus  formed  with 
three  liters  of  water.  Add  1,500  ml  of  solution  of  potassium 
oleate  (prepared  as  described  under  that  title).  Warm  the  mix- 
ture and  wash  the  separated  mercuric  oleate  twice  with  warm 
distilled  water,  using  about  one  liter  each  time.  Subject  the 
oleate  to  a  low  temperature  in  a  mortar,  and  then  press  out  of  it 
all  the  water  by  means  of  a  pestle. 

Reaction. 

Hg(N03)2+2KC18H3302=:Hg(C18H3302)2+2KN03. 

Notes.  Mercuric  chloride  cannot  be  employed  in  place  of  the 
nitrate,  nor  can  sodium  oleate  be  used  instead  of  the  potassium 
oleate,  as  the  washing  then  becomes  very  difficult. 


MERCURIC   OLEATE..  5OI 

The  yield  is  about  100  Gm  or  a  little  more.  The  product  is  a 
soft,  yellow  or  reddish  yellow  solid,  and  contains  28.4  per  cent  of 
mercuric  oxide. 

The  official  "oleate  of  mercury"  (U.  S.  P.),  is  a  soft  solid  made 
of  i  part  of  mercuric  oxide  and  4  parts  of  oleic  acid.  This  oleate 
is  best  prepared  at  not  over  40°  C.,  the  little  lumps  of  oxide  being 
carefully  broken  down  by  rubbing  between  two  horn  or  wooden 
spatulas,  two  or  three  times  a  day,  until  the  oxide  is  perfectly 
dissolved,  which  requires  8  or  10  days.  An  oleate  containing 
20  per  cent  of  oxide  keeps  fairly  well. 

When  small  quantities  are  made  the  oxide  and  oleic  acid  may 
be  mixed  in  a  porcelain  mortar  with  the  pestle. 

Mercuric  oleate  is  very  sensitive  to  heat,  decomposing  with  the 
separation  of  finely  divided,  dark  colored,  metallic  mercury.  Pre- 
cipitated oleate  of  mercury  containing  no  free  oleic  acid  keeps 
better  than  solutions  of  mercuric  oleate  in  free  oleic  acid,  and  the 
semi-solid  "20  per  cent  oleate"  keeps  better  than  the  liquid  "10. 
per  cent  oleate"  (containing  10  per  cent  of  oxide). 

Official  Oleate  of  Mercury. 

Yellow  mercuric  oxide,  thoroughly  dried .  .   200  Gm 
Oleic  acid 800  Gm 

Introduce  the  oleic  acid  into  a  capacious  mortar,  and  gradually 
add  to  it  the  yellow  mercuric  oxide  by  sifting  it  upon  the  surface 
of  the  acid,  and  incorporate  it  by  continuous  stirring.  Then  set 
the  mixture  aside  in  a  warm  place,  at  a  temperature  not  exceed- 
ing 40°  C.  and  stir  frequently,  until  the  oxide  is  dissolved. 

Description. — A  soft,  light  brownish-yellow  ointment-like 
solid. 

MERCURIC    OXIDE;    RED. 

HYDRARGYRI    OXIDUM    RUBRUM. 
HgO= 2 1 6. 

Dissolve  8  parts  of  mercury  in  9  parts  of  official  nitric  acid 
previously  diluted  with  4  parts  of  water.  Evaporate  the  solution 


5O2  MERCURIC    OXIDE. 

to  dryness.  To  the  residue  add  another  8  parts  of  mercury,  and 
triturate  in  a  mortar  until  metallic  globules  are  no  longer  visible 
and  the  mixture  appears  to  be  uniform.  Heat  this  mixture  in  a 
porcelain  dish  over  a  sand-bath,  stirring  frequently,  until  acid 
vapors  are  no  longer  evolved. 

Reactions. 

First,  3Hg+8HN03=3Hg ( NO3 ) 2+ 4H2O+2NO. 
Second,  Hg(N03)2+Hg=Hg2(N03)2. 
Third,  Hg2(NO3)2,  when  heated,  decomposes  into 
2HgC4-N204. 

Notes.  The  nitrate  is  decomposed  by  heat,  red  fumes  (nitrogen 
tetroxide)  being  evolved.  When  all  the  nitrate  has  been  thus 
decomposed,  the  acid  vapors  cease,  and  the  residue  is  mercuric 
oxide.  Care  must  be  taken  to  continue  the  heating  until  not  a 
trace  of  nitrate  remains.  Mercuric  oxide  when  strongly  heated 
becomes  very  dark,  but  the  red  color  returns  on  cooling.  If  the 
heat  is  too  high  (over  360°  C.)  the  oxide  decomposes  into  its 
elements,  wjiich  may  be  discovered  by  holding  a  piece  of  filter- 
paper  over  the  heated  mass,  when  metallic  mercury  will  condense 
on  the  paper. 

It  is  sometimes  directed  to  digest  the  residue  after  cooling,  with 
distilled  water  to  which  a  little  solution  of  soda  has  been  added, 
the  object  being  to  remove  any  remaining  nitrate.  In  this  case 
the  oxide  must  afterwards  be  thoroughly  washed,  and  dried  at  a 
gentle  heat. 

Description. — A  brick-red,  insoluble  powder.  Must  not  pro- 
duce red  vapors  when  heated.  It  is  completely  soluble  in  HC1, 
producing  HgCl2. 

Another  Method. 

A  finely  divided  red  mercuric  oxide  may  be  obtained  by  heating 
the  yellow  (precipitated)  mercuric  oxide  until  it  becomes  red 
on  cooling,  and  corresponds  to  the  pharmacopoeial  identity  tests. 


MERCURIC    OXIDE.  503 


MERCURIC    OXIDE;    YELLOW. 

HYDRARGYRI    OXIDUM    FLAVUM. 

[Precipitated  Mercuric  Oxide.] 
HgO=2i6. 

Mercuric   chloride 100  Gm 

Sodium    hydroxide 40  Gm 

Distilled  water,  sufficient. 

Dissolve  the  powdered  mercuric  chloride  in  3  liters  of  hot  dis- 
tilled water,  and  filter  the  solution. 

Dissolve  the  sodium  hydroxide  in  500  ml  distilled  water. 

Pour  the  solution  of  mercuric  chloride,  when  cold,  slowly  and 
in  a  small  stream,  or  a  little  at  a  time,  into  the  solution  of  sodium 
hydroxide,  stirring  briskly  and  uninterruptedly. 

Allow  the  mixture  to  stand  for  an  hour,  stirring  frequently. 

Decant  the  supernatant  liquid  from  the  precipitate,  and  wash 
the  latter  by  affusion  and  decantation  of  cold  distilled  water. 

Collect  the  precipitate  on  a  strainer  or  a  paper  filter  and  con- 
tinue the  washing  with  warm  distilled  water  until  a  portion  of 
the  washings  when  poured  over  a  little  test-solution  of  mercuric 
chloride  no  longer  produces  a  yellowish  turbidity  at  the  point  of 
contact  of  the  two  liquids. 

Then  allow  the  precipitate  to  drain,  and  dry  it  between  sheets 
of  white  blotting  paper,  in  a  dark  place,  at  a  temperature  not  ex- 
ceeding 30°  C. 

Keep  the  product  in  well-stoppered  bottles  in  a  dark  place. 
Reaction.     HgCl2+NaOH=HgO+2NaCl+H2O. 

Notes.  The  mercuric  chloride  is  used  in  the  form  of  powder 
and  hot  water  is  to  be  used  to  dissolve  it  in  order  to  save  time. 
But  the  solution  of  mercuric  chloride  must  be  cold  when  poured 
into  the  solution  of  sodium  hydroxide.  The  use  of  very  hot  so- 
lutions in  making  precipitated  mercuric  oxide  would  yield  a  prod- 
uct consisting  partly  of  the  red  variety.  The  use  of  a  too  high 
heat  in  washing  and  drying  yellow  oxide  of  mercury  is  to  be 
avoided  for  the  same  reason.  An  over-heated  freshly  precipi- 


504  MERCURIC    OXIDE. 

tated  mercuric  oxide  has  a  more  reddish  color  than  the  product 
not  exposed  to  a  too  high  temperature,  and  the  reddish  precipi- 
tated oxide  does  not  readily  form  mercuric  oxalate  when  treated 
with  a  strong  solution  of  oxalic  acid  as  described  in  the  Pharma- 
copoeia. 

As  mercuric  chloride  is  liable  to  contain  calomel,  the  omission 
of  the  nitration  might  result  in  the  discoloration  of  the  product 
by  the  mercurous  oxide  formed  by  that  calomel. 

The  sodium  hydroxide  used  should  contain  at  least  90  per  cent 
of  NaOH,  and  must  be  free  from  carbonate.  The  presence  of 
sodium  carbonate  in  the  "soda"  used  would  cause  the  formation  of 
mercuric  carbonate,  which  is  dark  browrn  and  usually  falls  after 
the  orange  yellow  mercuric  oxide  has  subsided  and  thus  forms  a 
thin  layer  over  the  oxide. 

Dilute  solutions  are  employed  because  the  use  of  a  strong  solu- 
tion of  mercuric  chloride  might  easily  lead  to  the  formation  of 
"oxychloride  of  mercury"  having  a  brown  or  brick-red  color. 
There  are  two  such  oxychlorides,  one  of  them  so  dark  brown  as  to 
appear  nearly  black  (HgQ2.2HgO),  and  the  other  brown-red  or 
brick-red  (HgCl2.3HgO).  In  order  to  prevent  the  formation 
of  either  of  these  oxychlorides  it  is  necessary  that  the  mercuric 
oxide  formed  should  not  be  permitted  to  come  in  contact  with  the 
mercuric  chloride.  Hence  the  mercuric  chloride  must  be  com- 
pletely decomposed  as  fast  as  it  is  added  to  the  solution  of  so- 
dium hydroxide.  This  result  is  insured  by  ( i )  making  the  solu- 
tion of  mercuric  chloride  very  dilute  while  the  solution  of  sodium 
hydroxide  is  less  diluted;  (2)  adding  the  solution  of  the  mer- 
curic chloride  to  the  solution  of  sodium  hydroxide,  instead  of 
vice  versa;  (3)  adding  the  mercury  solution  very  gradually; 
(4)  stirring  constantly  and  briskly  while  mixing  the  solutions ; 
and  using  a  larger  amount  of  sodium  hydroxide  than  required 
by  theory  according  to  the  chemical  equation,  so  that  the  alkali 
shall  be  in  excess  from  beginning  to  end. 

Should  the  solution  of  sodium  hydroxide  be  poured  into  that  of 
the  mercuric  chloride,  the  mercuric  oxide  then  formed  would  at 
once  (and  throughout  the  process  of  mixing  the  solutions)  come 
into  contact  with  the  mercuric  chloride,  and  would  then  form  oxy- 
chloride, which  would  be  evidenced  by  the  dark,  dirty  color  of  the 
precipitate. 

Should  mercuric  carbonate  or  any  oxychloride  be  formed,  caus- 


MERCURIC    OXIDE.  505 

ing  the  precipitate  to  appear  "off  color/'  they  may  be  decomposed 
by  maceration  with  an  excess  of  sodium  hydroxide.  Hence  the 
precaution  to  "let  the  mixture  stand  for  an  hour." 

But  if  the  mercuric  oxide  is  contaminated  with  oxychloride  or 
with  carbonate  it  usually  requires  a  stronger  solution  of  sodium 
hydroxide  and  longer  time  than  an  hour  to  insure  their  complete 
decomposition  and  the  final  formation  of  a  pure,  bright  orange- 
yellow  mercuric  oxide. 

Strict  observance  of  all  the  directions  here  given  as  to  the  degree 
of  dilution  of  the  solutions,  the  order  and  manner  of  mixing  them, 
and  the  purity  and  proportions  of  the  materials,  will  always  insure 
a  satisfactory  result. 

The  washing  is  to  be  continued  until  the  washings  are  free  from 
alkali.  The  washings  may  be  tested  for  sodium  hydroxide  in  the 
manner  prescribed,  or  for  sodium1  chloride  by  slightly  acidulating 
with  nitric  acid  and  then  using  test-solution  of  silver-nitrate. 

Light  affects  mercuric  oxide  comparatively  rapidly,  decom- 
posing it  into  metallic  mercury  and  oxygen.  Precipitated  mercuric 
oxide,  being  exceedingly  finely  divided,  is  more  rapidly  decom- 
posed than  the  red  mercuric  oxide.  The  metallic  mercury  formed 
by  the  reduction  is  also  extremely  finely  divided  and  hence  appears 
black,  thus  darkening  the  product.  Hence  the  light  should  be  en- 
tirely excluded  from  mercuric  oxide. 

Yellow  or  precipitated  mercuric  oxide  may  also  be  made  from 
an  acid  solution  of  mercuric  nitrate  instead  of  the  mercuric 
chloride,  and  potassium  hydroxide  may  be  used  in  the  place  of 
sodium  hydroxide. 

Description. — A  fine,  orange-yellow  powder,  amorphous,  very 
heavy,  odorless,  and  of  a  somewhat  metallic  taste.  Insoluble  in 
water  and  in  alcohol.  Darkens  on  exposure  to  air,  decomposing 
into  mercury,  mercurous  oxide,  and  oxygen. 

MERCURIC    PEPTONATE    SOLUTION. 

LIQUOR     HYDRARGYRI     PEPTONATI. 

1.  Make  a  solution  of  I  part  of  mercuric  chloride  in  20  parts 
of  distilled  water. 

2.  Dissolve  3  parts  of  dry  peptone  (free  from  sodium  chloride) 
in  10  parts  of  distilled  water. 


506  MERCURY    PEPTONATE. 

3.  Dissolve  I  part  of  sodium  chloride  in  50  parts  of  distilled 
water. 

Pour  solution  I  slowly  and  with  constant  stirring  into  solution 
2.  Let  the  mixture  stand  an  hour.  Collect  the  precipitate  on  a 
filter  and  let  it  drain  well.  Transfer  the  precipitate  to  a  porcelain 
dish,  add  solution  3  and  stir  well  until  solution  results.  Then 
add  enough  distilled  water  to  make  the  whole  product  weigh  100 
parts.  Filter. 

Keep  it  in  small,  completely  filled  and  well-stoppered  bottles 
in  a  cool,  dark  place. 

Description. — A  yellowish,  acid  liquid  of  disagreeable  metallic 
taste, 

MERCURIC   SALICYLATE. 

HYDRARGYRI     SALICYLAS. 

HgC7H403=336. 

Mercuric  chloride   27  parts 

Solution  of  sodium  hydroxide  (5%) .  . .  .  250  parts 

Salicylic  acid   15  parts 

Distilled  water,  sufficient. 

Dissolve  the  mercuric  chloride  in  540  parts  of  hot,  distilled 
water,  filter  the  solution,  and  let  it  cool  to  the  ordinary  room  tem- 
perature. 

Dilute  the  sodium  hydroxide  solution  with  50  parts  of  distilled 
water. 

Pour  the  cold  solution  of  mercuric  chloride  gradually  and  dur- 
ing uninterrupted  stirring  into  the  solution  of  sodium  hydroxide. 
Wash  the  precipitate  by  decantation  and  finally  on  a  paper  filter 
with  distilled  water  until  the  washings  give  no  further  reaction 
for  chloride. 

Collect  the  precipitate  and  put  it  in  a  flask  with  enough  distilled 
water  to  form  a  thin  mixture  when  shaken.  Then  add  the  salicylic 
acid,  shake  again  so  that  the  mixture  may  be  made  as  nearly  uni- 
form as  practicable,  and  then  heat  the  flask  on  a  water-bath, 
shaking  the  flask  frequently. 

When  the  yellow  color  of  the  mercuric  oxide  has  given  place  to 
the  pure  white  color  of  the  mercuric  salicylate,  which  is  the  finely 


MERCURIC    SALICYLATE.  507 

divided  insoluble  matter  now  contained  in  the  liquid,  remove  the 
flask  from  the  water-bath. 

Wash  the  mercuric  salicylate  with  hot  water  until  the  washings 
no  longer  give  an  acid  reaction  on  test-paper.  Then  collect  the 
product  on  a  paper  filter,  let  it  drain  well,  and  dry  it,  at  first  at  a 
moderate  heat  and  finally  at  100°  C. 

Notes.  The  salicylic  acid  is  used  in  slight  excess  and  forms 
mercuric  salicylate  with  the  freshly  precipitated  mercuric  oxide. 
The  excess  of  salicylic  acid  is  then  washed  out. 

Description. — A  white,  amorphous,  odorless  and  tasteless  pow- 
der, almost  insoluble  in  water  and  in  alcohol. 

Mercuric  salicylate  is  not  decomposed  by  carbonic  acid,  or  by 
tartaric,  lactic  or  acetic  acid,  nor  by  sodium  hydroxide  solution. 
When  the  salt  is  dissolved  in  a  solution  of  sodium  hydroxide  in 
such  proportion  that  one  molecule  of  NaOH  is  present  for  each 
molecule  of  HgC7H4O3,  a  double  salt  is  formed  which  crystallizes 
out  of  the  solution. 


MERCURIC   SULPHATE. 

HYDRARGYRI     SULPHAS. 


Mercury    ............................    100  Gm 

Sulphuric  acid   .......................     60  ml 

Heat  them  together  in  a  porcelain  capsulej  stirring  constantly, 
until  the  metal  disappears  and  a  "dry  white  salt  remains. 

Reaction.    Hg-f  2H2SO4=HgSO4+SO2-f  2H2O. 

Notes.     Mercury  is  insoluble  in  cold  sulphuric  acid. 

Mercuric  sulphate  is  used  in  the  preparation  of  calomel,  corro- 
sive sublimate,  and  basic  mercuric  sulphate. 

It  may  also  be  made,  as  described  in  the  next  paragraph,  with 
the  aid  of  nitric  acid,  when  less  sulphuric  acid  will  be  required. 

Description.  —  A  heavy  white  crystalline  powder  which  decom- 
poses on  the  addition  of  water,  yielding  yellow  subsulphate,  or 


5O8  MERCURIC    SULPHATE. 

Basic  Mercuric  Sulpjiate. 

HYDRARGYRI  SUBSULPHAS  FLAVUS. 

[Yellow  Subsulphate  of  Mercury.    Turpeth  Mineral. 


Mercury    ............................  100  Gm 

Sulphuric  acid   .......................  30  ml 

Nitric  acid    ..........................  25  ml 

Distilled  water,  sufficient. 

Put  the  mercury  in  a  roomy  flask,  add  the  sulphuric  acid,  pre- 
viously mixed  with  15  ml  of  distilled  water,  and  then  the  nitric 
acid,  previously  mixed  with  25  ml  of  distilled  water.  Digest  the 
mixture  at  a  gentle  heat  until  red  fumes  cease  to  be  given  off. 
Transfer  the  mixture  to  a  porcelain  dish  and  heat  it  on  a  sand-bath, 
under  a  hood  or  in  the  open  air,  with  frequent  stirring,  until  a 
dry,  white  salt  remains.  This  white  salt  is  normal  mercuric  sul- 
phate. Powder  this  and  throw  it,  in  small  portions  at  a  time,  into 
2  liters  of  boiling  distilled  water,  stirring  constantly.  Having 
added  all  of  the  mercuric  sulphate,  boil  the  mixture  ten  minutes, 
allow  it  to  settle,  decant  the  liquid,  transfer  the  precipitate  to  a 
filter,  wash  it  with  hot  distilled  water  until  the  washings  cease  to 
give  an  acid  reaction  on  test-paper,  and  finally  dry  the  product  in 
a  moderately  warm  place. 

Reaction.  2Hg+2H2SO4+2HNO8=2HgSO4+3H2O+N2O3- 
Then  the  mercuric  sulphate  is  split  up  by  water  into  a  basic  salt 
which  precipitates,  and  an  acid  salt  which  remains  in  solution, 
the  result  varying  somewhat  according  to  the  quantity  of  water 
used  and  its  temperature. 

Notes.  Mercuric  sulphate  can  be  made  from  mercury  and  sul- 
phuric acid  without  the  use  of  nitric  acid  ;  when  the  latter  is  added, 
however,  the  reaction  is  more  easily  accomplished. 

Basic  mercuric  sulphate  can  also  be  made  by  gradually  adding  a 
solution  of  mercuric  nitrate  to  a  solution  of  sodium  sulphate,  the 
latter  salt  to  be  in  excess. 

Description.  —  A  heavy,  lemon-yellow  powder,  odorless  and 
nearly  tasteless,  very  slightly  soluble  in  water,  insoluble  in  alcohol 


MERCURIC    SULPHIDE.  509 

or  ether.    When  heated  it  turns  red,  but  becomes  yellow  on  cool- 
ing. 

MERCURIC    SULPHIDE;  RED. 

HYDRARGYRI    SULPHIDUM  RUBRUM. 

(Vermillion.) 


Mercury    ..........................  .  150  parts 

Sulphur  ............................  57  parts 

Potassium  hydroxide    ................  38  parts 

Water. 

Triturate  the  mercury  with  the  sublimed  sulphur  until  no  more 
globules  of  mercury  are  visible  under  a  lens  of  ten  diameters 
magnifying  power. 

Dissolve  the  potassium  hydroxide  in  300  parts  of  water.  Add 
the  black  mercuric  sulphide  formed  by  the  trituration  of  the  metal 
with  the  sulphur.  Heat  at  45°  in  a  porcelain  dish  for  several 
hours,  stirring  briskly  at  frequent  intervals,  and  replace  the  water 
lost  by  evaporation  so  as  to  maintain  the  original  volume.  When 
the  powder  assumes  a  bright  scarlet  color,  t^irrr  the  contents  of 
the  dish  into  a  suitable  vessel  and  wash  the  sulphide  quickly  by 
affusion  and  decantation  of  warm  water  (having  a  temperature 
not  exceeding  45°),  until  the  washings  are  tasteless  and  quite 
neutral  to  test-paper.  Collect  the  product  on  a  strainer  or  filter, 
drain,  and  dry  it  at  from  45°  to  50°. 

Reactions.  Hg+S=HgS  ;  also  8KOH+4S==3K2S+K2SO4+ 
4H20. 

Notes.  The  quantity  of  sulphur  prescribed  in  this  formula 
(Brunner)  is  much  in  excess  of  that  accounted  for  by  the  forego- 
ing reactions  ;  the  excess  is  dissolved  by  the  solution  of  potassium 
sulphide,  perhaps  forming  hypothiosulpnite  and  tetrathiosulphate. 

It  is  not  underst  >od  why  the  black  mercuric  sulphide  made  by 
trituration  becomes  bright  scarlet  when  the  excess  of  sulphur  is 
removed  from  it  by  digestion  with  the  potassium  hydroxide. 

The  temperature  must  not  exceed  45°. 

As  continued  trituration  of  the  mercuric  sulphide  with  the 
solution  of  potassium  hydroxide  hastens  the  change  of  color  of 
the  product,  this  may  be  accomplished  in  the  same  mortar  in  which 


5IO  MERCURIC    SULPHIDE. 

the  black  sulphide  was  made,  provided  the  mortar  is  large  enough. 
It  should  be  kept  warm  by  placing  it  in  warm  water. 
The  yield  will  be  about  100  parts. 

Crude  Mercuric  Sulphide  (Mixed  with  Sulphur). 

(^Ethiops  Mineralis.) 

Mercury I  part 

Sulphur    i  part 

Triturate  them  together  in  a  glass  mortar  (or  in  a  glazed  por- 
celain mortar)  until  a  uniform  black  powder  shall  have  been  ob- 
tained in  which  no  globules  of  mercury  are  visible  under  a  lens  of 
ten  diameters  magnifying  power. 

Reaction.    Hg+S— HgS. 

Notes.  As  the  atomic  weight  of  mercury  is  200,  and  that  of 
sulphur  only  32,  it  follows  that  this  product  consists  of  about  3 
parts  of  mercuric  sulphide  and  2  parts  of  sulphur.  It  is  an  old 
preparation  formerly  employed  in  veterinary  medicine,  and  is 
included  in  this  book  simply  as  an  illustration  of  chemical  com- 
bination between  dry  solids  triturated  together. 

The  trituration  must  be  continued  at  least  two  hours  under 
strong  pressure.  This  necessarily  causes  the  formation  of  shining 
black  ''scales,"  which  must  finally  be  reduced  to  powder  by  gentler 
trituration  and  by  sifting  the  product  through  a  fine  sieve. 

The  mortar  and  pestle  are  at  the  end  of  the  trituration  covered 
with  a  black  coating  of  mercuric  sulphide  which  is  not  easily  re- 
moved if  the  mortar  used  be  one  made  of  wedgewood  ware  or 
other  porous  material.  Strong  nitric  acid  and  powdered  glass  or 
white  sand  may  be  triturated  together  in  the  mortar  to  remove  the 
stain. 

MERCUROUS   CHLORIDE. 

HYDRARGYRI     CHLORIDUM     MITE. 

(Calomel.    Mild  Mercurous  Chloride.) 

HgCl=235.2. 

Mercuric  sulphate  10  parts 

Mercury 7  parts 

Sodium  chloride,  dried 5  parts 

Boiling  distilled  water,  sufficient. 


CALOMEL.  511 

Moisten  the  mercuric  sulphate  with  some  of  the  water ;  add  the 
mercury ;  triturate  until  metallic  globules  are  no  longer  visible ; 
add  the  sodium  chloride  and  mix  the  whole  thoroughly  by  long 
continued  trituration.  Sublime  by  a  suitable  apparatus.  Wash 
the  sublimate  with  boiling  distilled  water  until  the  washings  cease 
to  be  darkened  by  a  drop  of  ammonium  hydrosulphide.  Dry  it  at 
not  over  100°  C. 

Reaction.  HgSO4+Hg=Hg2SO4;  then,  Hg2SO4+2NaCl= 
2HgCl+Na2SO4. 

Notes.  On  a  small  scale  the  sublimation  may  be  effected  in 
bottles  of  about  200  Cc.  capacity.  These  bottles  should  be  thin- 
bottomed  and  of  uniform  thickness,  and  should  have  rather  wide 
mouths.  During  the  process  of  sublimation  the  mouths  of  the 
bottles  may  be  closed  loosely  with  chalk  stoppers.  The  mixed 
powder  to  be  subjected  to  sublimation  must  be  thoroughly  dried 
before  it  is  put  into  the  bottles.  Flasks  or  retorts  may  also  be 
used.  The  bottles,  flasks,  or  retorts  are  heated  by  means  of  a 
sand-bath.  They  should  be  only  about  one-fourth  filled  and  buried 
into  the  sand  sufficiently  deeply  to  bring  the  level  of  the  contents 
of  the  subliming  vessel  below  the  level  of  the  sand  surrounding 
it.  The  heat  must  be  applied  caijtiously,  being  moderate  at  first, 
then  gradually  increased  until  the  calomel  has  all  been  sublimed. 

Sublimed  calomel  is  yellowish- white  when  prepared  in  small 
quantities  and  in  the  way  here  described.  When  manufactured 
on  a  large  scale,  the  vapor  is  rapidly  condensed  in  large  cham- 
bers into  which  steam  is  injected,  and  the  product  is  then  nearly 
or  quite  white  and  more  finely  divided. 

The  sublimate  obtained  in  operating  with  small  amounts  is 
crystalline  and  must  be  triturated  with  warm  water  a  long  time 
(levigated)  until  reduced  to  an  extremely  fine  (impalpable)  pow- 
der. The  warm  water  used  for  this  purpose  is  to  be  frequently 
changed  in  order  that  the  mercuric  chloride  may  be  effectually  re- 
moved from  the  calomel. 

The  heat  must  not  be  too  high  for  then  a  portion  of  the  calomel 
is  decomposed  into  mercury  and  mercuric  chloride. 

The  sublimate  formed  in  vessels  heated  in  a  sand-bath  is  de- 
posited immediately  above  the  level  of  the  sand  as  well  as  higher 
up.  To  remove  the  sublimate  it  is  necessary  to  break  the  vessel 


512  CALOMEL. 

containing  it.  Great  care  should  be  exercised  in  doing  this  so 
that  no  fragments  of  gla*ss  become  mixed  with  the  product.  If 
necessary  to  detach  the  crust  from  the  glass  while  the  sublimate 
is  still  warm,  it  is  best  to  moisten  it  a  little ;  but  after  a  few  days 
the  crust  can  be  readily  removed  without  being  moistened. 

All  sublimed  calomel,  however  made,  is  contaminated  with 
mercuric  chloride,  so  that  calomel  free  from  corrosive  sublimate 
can  be  obtained  only  by  levigating  the  sublimed  or  precipitated 
calomel  until  pure.  Elutriation  may  be  advantageously  combined 
with  the  levigation.  When  the  water  with  which  the  calomel  is 
levigated  ceases  to  become  darkened  by  ammonium  hydrosulphide 
or  to  be  rendered  unclear  on  the  addition  of  ammonia,  and  when 
the  wet  calomel  fails  to  produce  a  dark,  dull  spot  on  polished  steel 
after  five  minutes'  contact  with  it  the  product  is  free  from  mercuric 
chloride. 

Another  Method. 

Mercuric  chloride   : * 4  parts 

Mercury    3  parts 

Alcohol. 

Triturate  the  mercuric  chloride  and  mercury  together  in  a  por- 
celain mortar  until  all  metallic  globules  have  disappeared,  keeping 
the  mixture  moistened  all  the  time  with  some  alcohol  to  prevent 
the  poisonous  dust  from  rising.  When  no  more  mercury  globules 
are  visible  the  mixture  is  gray.  Put  the  gray  mixture,  still  damp 
from  the  alcohol  used,  in  a  porcelain  dish  and  heat  it  moderately 
upon  a  sand-bath,  with  constant  stirring,  until  the  moisture, 
mercuric  chloride,  and  mercury  have  been  expelled,  leaving  a 
yellowish-white  nearly  pure  calomel,  which  will  be  the  case  when 
a  white  sublimate  is  formed  on  the  bottom  of  a  flask  or  bottle  held 
immediately  above  the  contents  of  the  dish  when  strongly  heated. 
This  part  of  the  process  must  be  performed  under  a  hood  with  a 
good  draft,  or  in  any  manner  insuring  the  removal  of  the  poison- 
ous vapors  which  pass  off.  The  calomel  mixture,  thus  thoroughly 
dried  and  partially  freed  from  mercuric  chloride,  is  then  put  in 
bottles,  flasks,  or  retorts,  and  sublimed  as  described  in  the  notes 
under  the  preceding  process. 

Description. — A  heavy,  white,  impalpable  powder ;  odorless  and 
tasteless.  Becomes  yellowish-white  on  being  triturated  under 


CALOMEL.  513 

strong  pressure.  Should  show  only  isolated  crystals  under  a 
magnifying  power  of  one  hundred  diameters.  Insoluble  in  all 
simple  solvents.  Volatilizes  without  residue. 

When  exposed  to  light  it  turns  grayish  from  finely  divided 
metallic  mercury,  mercuric  chloride  being  at  the  same  time  formed. 
Calomel  must,  therefore,  be  kept  in  dark  amber-colored  bottles,  or 
otherwise  protected  from  the  light. 

Precipitated  Mercurous  Chloride.  F 

HYDRARGYRI   CHLORIDUM    MITE   PRAECIPITATUM. 

( Precipitated  Calomel. ) 

Mercury    175  parts 

Nitric  acid,  68%   150  parts 

Distilled  water,  sodium  chloride,  and  hydrochloric  acid. 

Put  the  mercury  in  a  tared  flask ;  add  100  parts  nitric  acid  and 
150  parts  water.  Heat  the  flask  moderately  on  a  sand-bath,  cover- 
ing the  mouth  of  the  flask  with  a  watch-glass,  and  continue  the 
heat  without  interruption  for  one  hour  after  red  fumes  have  ceased 
to  be  evolved,  or  until  the  liquid  begins  to  acquire  a  yellowish  color 
and  to  become  slightly  turbid.  Pour  the  solution  of  mercurous 
nitrate  off  from  the  undissolved  mercury. 

Mix  50  parts  of  nitric  acid  with  1000  parts  of  boiling  distilled 
water,  and  add  this  mixture  to  the  solution  of  mercurous  nitrate 
while  still  hot.  Let  the  mixture  cool. 

Test  the  liquid  to  ascertain  whether  or  not  it  will  bear  dilution 
with  an  equal  volume  of  cold  distilled  water  without  becoming 
turbid.  To  perform  this  test  mix  about  5  ml  of  the  solution  with 
5  ml  of  distilled  water.  Should  the  mixture  remain  clear,  return 
it  to  the  whole  quantity  of  the  mercury  solution.  Should  it  become 
turbid,  add  a  sufficient  quantity  of  nitric  acid  to  the  whole  solu- 
tion to  acidify  it  so  that  dilution  with  twice  its  volume  of  water 
without  precipitation  is  rendered  assured. 

Ascertain  the  quantity  of  mercury  contained  in  the  solution  by 
deducting  from  the  quantity  originally  taken  the  weight  of  the 
undissolved  portion  remaining  in  the  flask.  [That  undissolved 
mercury  must  be  washed  and  dried  before  weighing  it.] 

Take  a  quantity  of  sodium  chloride  equal  to  the  weight  of  the 
dissolved  mercury;  dissolve  that  sodium  chloride  in  20  times  its 

Vol.    11—33 


514  CALOMEL. 

weight  of  distilled  water,  and  add  to  this  solution  5  per  cent  of 
its  weight  of  hydrochloric  acid.  Then  pour  the  sodium  chloride 
solution  gradually  into  the  mercury  solution,  stirring  constantly. 

Wash  the1  precipitate  with  cold  distilled  water,  by  affusion  and 
decantation,  until  the  washings  no  longer  give  an  acid  reaction  on 
test-paper. 

Dry  the  product  at  a  temperature  not  exceeding  40°  C. 

Reactions.  3Hg+4HNO8=3HgNO8+2H2O+NO,  and  sub- 
sequently HgNO8+NaCl=HgCl+NaNO:{. 

Notes.  It  is  necessary  that  the  mercury  solution  should  contain 
enough  nitric  acid  to  remain  clear  when  diluted  with  its  own  vol- 
ume of.  water,  and  it  is  to  be  tested  to  make  sure  of  that  fact  before 
the  solution  of  sodium  chloride  is  added,  because  if  the  mercury 
solution  should  contain  too  little  nitric  acid  the  precipitate  formed 
upon  dilution  with  water  is  a  basic  mercurous  nitrate  and  this 
would  then  be  precipitated  by  the  solution  of  sodium  chloride 
together  with  the  calomel.  But  if  the  solution  of  mercurous  ni- 
trate will  bear  dilution  with  its  own  volume  of  water  without 
becoming  turbid,  it  may  safely  be  mixed  with  more  than  its  own 
volume  of  sodium  chloride  solution,  gradually  added,  without  any 
danger  of  the  precipitation  of  basic  mercurous  nitrate  together 
with  the  mercurous  chloride. 

The  large  dilution  of  the  liquids  is  necessary  to  prevent  'the  for- 
mation of  mercuric  salts  by  the  nitric  acid. 

Precipitated  calomel  is  much  bulkier  than  sublimed  calomel,  and 
is  extremely  finely  divided. 

It  should  be  tested  for  nitrate,  from  which  it  must  be  quite 
free. 

Another  Method. 

Dissolve  i  part  of  mercuric  chloride  in  50  parts  of  distilled 
water.  Keep  the  solution  at  a  temperature  of  from  70°  to  80°  C., 
and  conduct  into  it  a  current  of  washed  sulphur  dioxide  (prepared 
from  sodium  bisulphite  and  diluted  sulphuric  acid  as  described 
under  the  title  of  sulphurous  acid,  until  saturated  with  it.  Let 
the  liquid  cool.  Wash  the  precipitated  calomel  upon  a  filter  with 
distilled  water.  Dry  the  product  with  the  aid  of  gentle  heat. 

Reaction.     2HgCl2+SO2+2H2O— 2HgCl+H2SO4+2HCl. 


MERCURIUS    SOLUBILIS.  515 

Description. — See  sublimed  calomel.  The  only  differences  be- 
tween sublimed  calomel  and  precipitated  calomel  is  that  the  latter 
is  lighter  (bulkier),  being  finer,  and  less  liable  to  contain  crystals 
(visible  under  the  microscope,  only). 

Mercurius  Solubilis  Hahnemanni. 
[Nitras  amido-hydrargyricus  cum  hydrargyro;  Danish  Ph.] 

Mercurous  nitrate    180      parts 

Nitric  acid 12.8  parts 

Ammonia  water   100      parts 

"  Alcohol    1 150      parts 

Distilled  wat^r,  sufficient. 

Dissolve  the  mercurous  nitrate  in  a  cold  mixture  of  the  nitric 
acid  with  1800  parts  of  distilled  water.  Pour  this  solution  slowly 
into  a  mixture  of  the  ammonia  water  and  alcohol,  stirring  con- 
stantly. 

[The  mixture  thus  obtained  should  have  a  feebly  acid  reaction.] 

Collect  the  precipitate  on  a  filter,  let  it  drain,  and  wash  it  with  a 
small  quantity  of  alcohol.  Dry  it  in  a  dark  place  and  without  the 
aid  of  heat. 

Must  be  protected  from  the  light. 

Description. — A  heavy,  dead  black,  fine  powder,  odorless,  taste- 
less, insoluble  in  water  and  in  alcohol.  Heated  to  a  high  tempera- 
ture it  decomposes,  giving  off  nitrous  vapors,  and  leaves  no  fixed 
residue.  Heated  with  sodium  hydroxide  solution  it  gives  off  am- 
monia. Should  be  completely  soluble  in  nitric  acid. 

MERCUROUS  IODIDE. 

HYDRAGYRI   IODIDUM   FLAVUM. 

Yellow  Iodide  of  Mercury. 
Hgl=326.5. 

Mercury 8  parts 

Iodine    5  Parts 

Alcohol. 

Triturate  the  iodine  in  a  glazed  porcelain  mortar  ( or  in  a  glass 


516  MERCUROUS  IODIDE. 

mortar)  with  three  parts  of  alcohol.  Add  the  mercury,  Con- 
tinue the  trituration  until  all  globules  of  mercury  have  disappeared 
and  the  mixture,  when  nearly  dry,  has  acquired  a  greenish-yellow 
color.  During  the  trituration,  add  more  alcohol,  from  time  to 
time,  as  may  be  necessary  to  keep  the  mixture  constantly  moist. 

When  the  reaction  is  at  an  end,  as  indicated  by  the  disappear- 
ance of  mercury  globules  and  by  the  development  of  a  greenish- 
yellow  color,  add  enough  alcohol  to  reduce  the  whole  to  a  thin  mix- 
ture, liquid  enough  to  be  poured  into  a  bottle.  Use  sufficient  addi- 
tional small  portions  of  alcohol  to  rinse  the  mortar  well  and  to 
transfer  all  of  the  wet  powder  to  the  same  bottle. 

Cork  the  bottle  and  set  it  aside  in  a  dark  but  moderately  warm 
place  for  a  day,  shaking  it  occasionally  during  that  period.  Then 
let  the  heavy  powder  subside  completely,  pour  off  the  alcohol  from 
the  solid  matter  and  add,  instead  of  the  alcohol  thus  decanted, 
about  50  parts  of  pure  alcohol,  warm  the  bottle,  shake  well,  and 
again  set  it  aside,  well  corked,  for  a  day  or  two. 

Decant  again,  and,  if  necessary,  repeat  once  more  the  washing 
of  the  mercurous  iodide  with  another  portion  of  warm  alcohol. 

Finally  shake  the  bottle  well,  transfer  its  contents  to  a  white 
paper  filter,  and  continue  washing  the  product  on  the  filter  with 
warm  alcohol  until  the  washings  are  no  longer  darkened  by  hydro- 
gen sulphide  or  by  a  weak  solution  of  sulphurated  potassa. 

When  the. washing  shall  have  been  completed  as  described,  dry 
the  product  between  white  blotting  paper  in  a  dark  place  at  a 
temperature  not  exceeding  40°. 

Keep  the  product  in  a  well-closed  bottle  and  protected  from 
light. 

Reaction.    Hg+I=HgI. 

Notes.  The  reaction  between  the  two  elements  causes  much 
'heat.  The  alcohol  added  before  and  during  the  trituration  is 
/  evaporated  by  this  heat,  and  thus  keeps  the  temperature  down  so 
as  to  prevent  the  loss  of  iodine  by  vaporization,  which  would  be 
sustained  were  the  materials  triturated  together  in  a  dry  state. 
But  the  reaction  is  not  complete.  The  product  obtained  by  this 
method  contains  mercury  and  mercuric  iodide  as  well  as  mercnrous 
iodide.  The  mercury  cannot  be  removed,  and  its  presence  gives 
the  mercurous  iodide  a  greenish  hue.  Pure  mercurous  iodide  is 


MERCUROUS  IODIDE.  517 

yellow  without  greenish  tint.  The  mercuric  iodide  is  washed  out 
with  warm  alcohol. 

The  alcohol  used  for  washing  out  the  mercuric  iodide  may  all 
be  recovered  by  distillation  after  adding  some  solution  of  potas- 
sium hydroxide. 

The  best  method  for  the  preparation  of  mercurous  iodide  is  by 
the  decomposition  of  mercurous  nitrate  with  potassium  iodide. 

Another  Method. 

Mercury    4  parts 

Mercuric  iodide 9  parts 

Alcohol,  sufficient. 

Triturate  the  metal  with  the  mercuric  iodide,  keeping  the  mix- 
ture constantly  moist  with  alcohol,  until  no  more  mercury  globules 
can  be  detected  with  a  lens  of  ten  diameters  magnifying  power. 
Wash  the  greenish-yellow  powder  by  digestion  with  warm  alcohol 
until  the  washings  are  no  longer  darkened  by  hydrogen  sulphide. 

Reaction.     HgI2+Hg=HgI. 

Notes.  Compare  this  method  with  the  one  immediately  preced- 
ing it. 

Official  Method;  U.  S.  P. 

Mercury 50  Gm 

Nitric  acid, 
Potassium  iodide, 
Distilled  water, 
Alcohol. 

Mix  20  ml,  each,  of  nitric  acid  and  distilled  water,  and,  when 
the  liquid  is  cold,  pour  it  upon  the  mercury  contained  in  a  small 
glass  flask.  Set  the  mixture  aside  in  a  cool  and  dark  place,  and 
agitate  it  occasionally,  until  the  reaction  ceases,  and  a  little  mer- 
cury still  remains  undissolved.  Separate  the  crystals  of  mercurous 
nitrate,  which  will  have  formed,  from  the  mother-liquid,  allow 
them  to  drain  in  a  glass  funnel,  and  dry  them  on  bibulous  paper, 
in  a  dark  place.  When  the  salt  is  dry,  weigh  off  40  Gm  of  it,  and 
dissolve  it  in  i  liter  of  distilled  water  to  which  10  ml  of  nitric  acid 
had  previously  been  added.  Having  prepared  a  solution  of  24 
Gm  of  potassium  iodide  in  i  liter  of  distilled  water,  slowly  pour  the 


5l8  MERCUROUS  IODIDE. 

solution  of  potassium  iodide  into  that  of  the  mercurous  nitrate, 
with  constant  stirring,  allow  the  precipitate  to  subside,  decant 
the  supernatant  liquid,  and  transfer  the  precipitate,  together  with 
the  remainder  of  the  liquid,  to  a  filter.  When  the  precipitate  has 
drained,  wash  it  with  distilled  water  until  the  washings  no  longer 
have  an  acid  reaction  upon  litmus  paper,  and  afterwards  wash  it 
with  alcohol,  as  long  as  the  clear,  colorless  washings  give  any 
color  with  hydrogen  sulphide  test-solution.  Lastly,  dry  the 
product  in  a  dark  place,  between  sheets  of  bibulous  paper,  at  a 
temperature  not  exceeding  40°  C. 

Keep  it  in  dark,  amber-colored  bottles,  with  the  least  possible 
exposure  to  light. 

Reactions.  3Hg+4HNO8=3HgNO8+2H2O+NO  ;  and,  then, 
HgN03+KI=HgI+KN03. 

Notes.  The  preparation  of  mercurous  nitrate  is  described  else- 
where. Instead  of  adding  the  mercury  nitrate  to  the  potassium 
iodide,  which  would  cause  the  precipitation  of  some  basic  mer- 
curous nitrate  with  the  mercurous  iodide,  it  is  necessary  that  the 
usual  order  of  mixing  the  reagents  be  reversed  in  this  case ; 
hence  the  formula  directs  that  the  solution  of  potassium 
iodide  be  added  to  the  solution  of  mercurous  nitrate.  The  precip- 
itated mercurous  iodide  is  light  yellow.  It  should  be  protected 
against  light  throughout  the  process  of  preparation  as  well  as 
afterwards.  The  mercuric  iodide  which  is  formed  with  the  mer- 
curous iodide,  owing  to  the  presence  of  mercuric  nitrate  and  nitric 
acid  with  the  mercurous  nitrate,  is  washed  out  with  alcohol. 

Instead  of  weighing  off  40  Gm  of  the  mercurous  nitrate  as  above 
directed,  the  whole  of  the  crystallized  salt  may  be  taken  and  the 
amount  of  potassium  iodide,  etc.,  adjusted  in  accordance  with  the 
proportions  given  above. 

Description. — A  bright  yellow,  amorphous,  odorless,  tasteless, 
insoluble,  heavy  powder.  Darkens  on  exposure  to  light,  decom- 
posing into  mercuric  iodide  and  mercury. 

Made  by  triturating  mercury  and  iodine,  or  mercury  and  mer- 
curic iodide,  together,  the  preparation  is  invariably  yellowish- 
green  because  the  reaction  is  not  complete  so  that  the  product 
contains  mercuric  as  well  as  mercurous  iodide  and  mercury. 


A1ERCUROUS   NITRATE.  gtC) 

MERCUROUS   NITRATE. 

HYDRARGYROSUS     NITRAS. 

HgNO3.H2O=28o. 

Add  a  cold  mixture  of  30  parts  of  nitric  acid  and  20  parts  of 
distilled  water  to  55  parts  of  mercury,  in  a  flask.  Let  the  mixture 
stand  in  a  dark  place,  agitating  it  occasionally,  until  reaction  ceases 
and  but  little  of  the  metal  remains  undissolved.  Collect  in  a  glass 
funnel  the  crystals  of  mercurous  nitrate  which  have  been  formed 
in  the  cold  liquid,  and  allow  them  to  drain.  Then  place  the  crys- 
tals on  white  blotting  paper  and  dry  them- in  a  dark  place. 

Reaction.     3Hg+4HNO,= 3HgNO3+2H2O+NO. 

Notes.  The  mercury  nitrate  remaining  in  the  mother  liquid 
should  be  recovered  as  well  as  the  undissolved  mercury.  The  ra- 
tionale of  the  process  is  the  formation  of  normal  mercurous  nitrate 
in  solution  in  a  mixture  of  nitric  acid  and  water,  employing  so 
small  a  quantity  of  liquid  that  the  greater  part  of  the  salt  crystal- 
lizes out. 

By  digestion  of  an  excess  of  mercury  with  the  acid  and  water, 
or  with  the  acid  solution  of  mercurous  nitrate,  a  basic  mercurous 
salt  would  soon  be  formed,  which  separates  in  pale  yellow  crystals 
or  powder.  An  experienced  operator  may  employ  digestion  and 
continue  it  until  basic  mercurous  nitrate  begins  to  deposit,  after 
which  the  solution  should  be  decanted,  a  little  nitric  acid  added  to 
it,  and  the  clear  liquid  set  aside  in  a  cold  place  that  crystals  may  be 
formed. 

Mercury  dissolves  in  nitric  acid  with  greater  or  less  rapidity  ac- 
cording to  the  temperature  and  the  degree  of  concentration  of  the 
acid.  When  strong  nitric  acid  is  used  the  solution  will  contain 
mercuric  nitrate,  which,  however,  is  reduced  to  mercurous  nitrate 
by  digestion  with  more  mercury. 

By  dissolving  mercury  in  cold  dilute  nitric  acid,  mercurous 
nitrate  is  obtained. 

The  acid  should  be  present  in  excess,  because  otherwise  basic 
salts  are  formed  which  are  insoluble  in  the  liquid. 

Normal  mercurous  nitrate  may  be  obtained  from  the  solution  in 
colorless  plates  which  can  be  dissolved  in  a  small  quantity  of 


520  MERCUROUS    NITRATE. 

water,  but  which  decompose  if  much  water  is  added,  an  acid  mer- 
curous  nitrate  remaining  in  solution  whilst  a  yellow  basic  mer- 
curous nitrate  precipitates. 

A  dilute  solution  of  mercurous  nitrate  can  therefore  not  be  made 
without  an  excess  of  nitric  acid. 

Description. — Colorless  crystals,  which  partially  effloresce  on 
exposure  to  air,  and,  when  heated,  first  fuse  and  then  volatilize 
without  residue.  Soluble  without  decomposition  in  a  small  quan- 
tity of  warm  water ;  easily  soluble  in  diluted  nitric  acid.  A  larger 
proportion  of  water  decomposes  the  salt,  causing  the  formation  of 
a  light  yellow  basic  mercurous  nitrate. 

Tests.  A  solution  of  the  salt  in  water  strongly  acidulated  with 
nitric  acid  gives  a  black  precipitate  with  solution  of  sodium  hy- 
droxide, and  a  white  precipitate  with  hydrochloric  acid. 

When  five  hundred  milligrams  of  the  salt  is  triturated  with  two 
hundred  and  fifty  milligrams  of  sodium  chloride  and  water  is 
added,  the  filtrate  obtained  from  this  mixture  is  darkened  on  the 
addition  of  hydrogen  sulphide,  but  should  not  give  a  precipitate 
with  that  reagent  (absence  of  mercuric  nitrate). 

MERCUROUS    OXIDE. 

HYDRARGYRI     OXIDUM     NIGRUM. 
Hg2O=4l6. 

Prepared  by  macerating  freshly  precipitated  mercurous  chloride 
with  solution  of  potassium  hydroxide  in  excess.  The  thoroughly 
washed  and  still  moist  mercurous  chloride  is  gradually  added  to 
the  solution  of  potassa,  with  diligent  stirring;  the  whole  is  well 
shaken,  and  then  set  aside  in  a  dark  place  until  the  black  mercurous 
oxide  has  settled.  This  is  then  washed  with  cold  distilled  water, 
collected,  and  dried  between  folds  of  blotting  paper  in  a  cool,  dark 
place. 

Must  be  kept  well  protected  from  the  light. 

About  12  parts  of  precipitated  calomel,  and  24  parts  of  solution 
of  potassium  hydroxide  of  1.33  specific  weight,  will  be  required  to 
prepare  10  parts  of  mercurous  oxide. 

Solution  of  sodium  hydroxide  may  be  used  instead  of  the  solu- 
tion of  potassium  hydroxide. 


MERCUROUS  TANNATE.  521 

MERCUROUS    TANNATE. 

HYDRARGYRI    TANNATUM. 

Mercuous  nitrate.  .  .  .  f.  ................   50  parts 

Tannic  acid  ...........................   30  parts 

Distilled  water,  sufficient. 

Triturate  the  dry  mercurous  nitrate  in  a  porcelain  mortar  until 
reduced  to  as  fine  powder  as  possible. 

Triturate  the  tannic  acid  with  50  parts  of  distilled  water  to  a 
uniform  and  smooth  mixture. 

Add  the  tannin  mixture  to  the  powdered  mercurous  nitrate  and 
triturate  together  until  a  perfectly  uniform  soft  mass  is  obtained, 
entirely  free  from  hard  particles.  Then  add  gradually  during 
constant  trituration  enough  distilled  water  to  produce  a  thin  mix- 
ture and  pour  that  into  3,000  parts  of  distilled  water.  Wash  the 
greenish  precipitate  with  cold  water  by  decantation  and  finally 
on  a  strainer  or  on  a  paper  filter  until  the  washings  are  free  from 
nitric  acid.  Dry  the  precipitate  on  filter  paper  spread  upon  porous 
tiles,  or  on  several  thicknesses  of  white  blotting  paper,  and  finally 
by  the  aid  of  heat  not  exceeding  40°  C. 

Must  be  protected  from  light. 

Notes.  The  composition  of  the  product  is  not  definite,  but  it  is 
believed  to  contain  about  50  per  cent  of  Hg. 

At  temperatures  above  40°  C.  the  moist  precipitate  is  liable 
to  cake  together. 

It  must  be  well  dried  in  order  to  keep. 

Description.  —  Brownish-green  masses,  odorless,  tasteless,  insol- 
uble in  water  and  in  alcohol. 

OXYGEN. 

OXYGENIUM. 


Potassium   chlorate  ....................    10  parts 

Manganese  dioxide  ....................     3  parts 

Sodium  carbonate  .....................     2  parts 


522  OXYGEN. 

Fuse  the  sodium  carbonate  in  its  own  water  of  crystallization; 
add  the  potassium  chlorate ;  mix  well ;  evaporate  to  dryness,  and 
powder  the  mass.  Mix  this  powder  intimately  with  the  powdered 
manganese  dioxide.  Put  the  mixture  in  a  suitable  flask  provided 
with  delivery-tube  and  safety  tubCj  and  heat  the  contents  over 
a  Bunsen  burner.  The  generator  or  flask  should  be  connected 
with  a  wash-bottle  containing  water. 

The  reaction  is  :     2KC1O3=2KC1+3O2. 

Notes.  The  manganese  dioxide  causes  the  potassium  chlorate 
to  decompose  more  quietly  and  at  a  lower  temperature,  than  would 
be  the  case  when  the  chlorate  is  heated  alone.  The  sodium  car- 
bonate also  facilitates  the  regularity  of  the  decomposition  of  the 
chlorate  and  prevents  the  formation  of  gaseous  chlorine  oxides 
which  are  liable  to  contaminate  the  oxygen.  As  a  further  precau- 
tion the  gas  is  washed  by  passing  it  through  water. 

The  manganese  dioxide  must  be  free  from  carbon  (powdered 
coal)  and  organic  matter,  and  the  materials  perfectly  dry. 

The  retort,  Fig.  120,  p.  184,  may  be  used. 

One  kilogram  of  KC1O3  should  furnish  about  240  liters  of 
oxygen. 

One  cubic-decimeter  of  oxygen  at  o°  C,  bar.  760  mm,  weighs 
about  1.43  Gm,  so  that  i  Gm  of  oxygen  under  those  conditions 
occupies  the  volume  of  about  699  cubic-centimeters. 

PHOSPHORUS. 

Phosphorus  for  medicinal  and  pharmaceutical  uses  should  be 
white.  It  is  preserved  in  glass-stoppered  bottles  filled  with  water, 
which  should  be  put  in  a  place  where  there  is  no  danger  that  they 
may  be  broken. 

Phosphorated  OIL 

OLEUM    PHOSPHORATUM  ;    U.    S. 

Introduce  about  100  Gm  of  almond  oil  into  a  flask  and  heat  it 
for  fifteen  minutes  over  a  sand-bath  at  a  temperature  of  250°  C. 
Allow  it  to  cool  to  about  60°  C.?  and  then  filter  it.  Put  90 
Gm  of  this  filtered  oil  into  a  dry  and  tared  bottle  of  about 
1 20  Cc  capacity.  Add  i  Gm  of  phosphorus  previously  well 


PHOSPHORATED  OIL.  523 

dried  by  gently  touching  it  with  white  blotting  p^per.  Close 
the  bottle  with  a  glass  stopper  and  heat  it  in  a  water-bath 
until  the  phosphorus  melts.  Then  shake  until  the  phosphorus 
has  dissolved,  allow  it  to  cool,  and  add  enough  ether  to  make  the 
total  contents  of  the  bottle  weigh  100  Gm.  Shake  again. 

Keep  the  product  in  glass-stoppered  bottles  of  about  30  Cc 
capacity,  completely  filled,  and  put  in  a  cool  and  dark  place. 

Notes.  Keeping  the  oil  of  almond  at  the  high  temperature 
prescribed  for  fifteen  minutes  expels  moisture  and  air  from  it, 
and  also  causes  the  separation  of  some  organic  matters,  which 
deposit  in  the  form  of  a  flocculent  sediment  on  cooling  and  are 
then  filtered  out.  The  oil  thus  prepared  is  nearly  colorless. 

The  phosphorus  used  should  be  clean,  translucent  pieces. 

The  ether  used  should  be  of  the  official  strength ;  ordinary  com- 
mercial ether  would  render  the  preparation  unclear. 

At  a  too  low  temperature  the  phosphorus  crystallizes  out;  this 
should  be  carefully  guarded  against,  and  when  it  occurs  it  should 
not  escape  observation.  The  separated  phosphorus  may  be  readily 
redissolved  by  gently  warming  and  shaking. 

The  preparation  is  not  phosphorescent  in  the  dark. 

PLATINUM  .CHLORIDE. 

CHLOROPLATINIC    ACID. 

H2PtCl6.6H20=5i6.4. 

Dissolve  platinum  scraps  .in  a  mixture  of  I  part  of  strong  nitric 
acid  and  5  parts  of  strong  hydrochloric  acid.  Evaporate  to  dry- 
ness.  Dissolve  the  residue  in  hot  water,  adding  a  little  hydro- 
chloric acid.  Add  an  excess  of  sodium  hydroxide  solution.  Boil 
the  mixture  for  about  an  hour,  adding  a  few  drops  of  alcohol. 
Redissolve  the  precipitate  in  hydrochloric  acid,  filter,  and  add  a 
hot  saturated  solution  of  ammonium  chloride  as  long  as  it  causes 
precipitation  of  ammonium-platinum  chloride  (or  ammonium 
chloroplatinate).  Collect  the  yellow  precipitate  and  wash  it  with 
cold  and  very  dilute  hydrochloric  acid.  Then  dry  it  in  a  por- 
celain dish  or  on  glass.  Heat  it  in  a  porcelain  crucible  until  re- 
duced. When  no  more  ammonia  or  chlorine  is  evolved,  dissolve 
the  metal  again  in  a  mixture  of  strong  hydrochloric  and  nitric 


524  CHLOROPLATINIC   ACID. 

acids,  in  the  same  proportions  as  before,  evaporate  to  dryness, 
adding  hydrochloric  acid  from  time  to  time  until  all  nitric  acid 
shall  have  been  expelled.  Redissolve  the  residue  in  hydrochloric 
acid  and  evaporate  to  crystallization. 

Notes.  The  object  of  treating  the  first  solution  with  sodium 
hydroxide  at  boiling  heat  is  to  reduce  any  iridium  tetrachloride 
present  to  trichloride,  which  afterwards  forms  a  soluble  double- 
salt  with  ammonium  chloride  when  the  ammonium  chloroplatin- 
ate  is  precipitated.  The  alcohol  added  during  the  treatment  with 
NaOH  is  to  decompose  any  sodium  hypochlorite  formed. 

The  evaporation  to  crystallization  may  be  advantageously  com- 
pleted over  concentrated  sulphuric  acid  or  lime  in  a  desiccator. 

Description. — Chloroplatinic  acid  is  a  yellow  deliquescent  salt, 
soluble  in  alcohol  as  well  as  in  water.  It  is  considered  as  formed 
by  the  direct  union  of  platinum  tetrachloride  and  hydrochloric 
acid. 

POTASSIUM   ACETATE. 

POTASSII    ACETAS. 

KC2H3O2=98. 

Acetic  acid 5  parts 

Potassium   bicarbonate 3  parts 

Add  the  potassium  bicarbonate  gradually  to  the  acid;  filter; 
evaporate  over  a  sand-bath  to  dryness,  stirring  constantly,  adding 
a  little  acetic  acid  if  necessary  to  keep  it  in  decided  excess  to  the 
end. 

Must  be  kept  in  tightly  corked  bottles. 

Reaction.     KHCO3+HC2H3O2=:KC2H3O2+CO2+H2O. 

Notes.  Theoretically  the  proportions  given  in  the  foregoing 
formula  leave  the  acetic  acid  slightly  in  excess;  but  this  excess 
of  acid  will  be  driven  off  during  the  evaporation,  and  more  must 
be  added  from  time  to  time  as  may  be  required  in  order  to  main- 
tain a  slightly  acid  reaction. 

The  temperature  during  the  evaporation  should  be  120°  to 
140°  C. 


POTASSIUM    ACETATE.  525 

Second  Method. 
Another  method  of  preparation  is  as  follows: 

Lead  acetate 13  parts 

Potassium   bicarbonate 7  parts 

Dissolve  each  salt  in  about  40  parts  of  water,  filter,  and  add 
the  solution  of  lead  acetate  to  that  of  the  potassium  bicarbonate, 
stirring  well.  Let  settle.  Decant  the  supernatant  liquid  which 
contains  the  potassium  acetate,  add  enough  acetic  acid  to  it  to 
render  it  slightly  acid,  and  evaporate  to  dryness. 

Collect  and  wash  the  precipitated  lead  carbonate. 

Reaction. 

3Pb(C2H302)2+6KHC03 

-2PbC03.Pb(OH)2+6KC2H302+2H20+4C02 

Description. — A  white  powder  or  feathery  crystalline  salt  of 
satiny  lustre.  Odorless.  Taste  saline,  wrarming.  Very  deli- 
quescent. Soluble  in  0.36  part  of  water  and  in  1.9  parts  of 
alcohol  at  15°. 

POTASSIUM  ANTIMONATE. 

POTASSII    ANTIMONAS. 

Metallic  antimony I  part 

Potassium   nitrate 2  parts 

Powder  each  substance  separately.  Mix  them  well.  Put  the 
mixture,  a  small  portion  at  a  time,  in  a  crucible  heated  to  dull 
redness.  When  all  has  been  added  continue  the  heating  for  half 
an  hour  after  the  completion  of  the  detonation  of  the  mixture, 
taking  care  not  to  allow  the  contents  of  the  crucible  to  fuse.  Let 
cool.  Powder  the  mass,  wash  the  powder  well  with  distilled 
water,  and  then  dry  the  product. 

Notes.  When  antimony  is  strongly  heated  with  potassium 
nitrate  the  metal  decomposes  the  nitrate  and  a  salt  is  formed 
which  was  at  one  time  official  in  some  pharmacopoeias  under  the 
title  of  "superstibias  kalicus,"  or  acid  potassium  antimonate. 


526  POTASSIUM  ANTIMONATE. 

If  the  mixture  of  the  antimony  and  potassium  nitrate,  after 
detonation,  should  be  heated  to  so  high  a  temperature  that  the 
mass  undergoes  fusion,  the  product  is  not  the  same,  being  water- 
soluble. 

The  composition  is  uncertain. 

Description. — A  white  or  but  slightly  yellowish  powder,  insol- 
uble in  water.  [If  the  antimony  was  free  from  iron  the  product 
is  white.] 


POTASSIUM    ARSENITE    SOLUTION. 

LIQUOR    POTASSII    ARSENITIS. 

[Liquor  Arsenicalis.     Fowler's  Solution.] 

Arsenous  oxide,  in  fine  powder 10  Gm 

Potassium    bicarbonate 20  Gm 

Compound  tincture  of  lavender 30  ml 

Distilled  water,  sufficient. 

Boil  the  arsenous  oxide  and  potassium  bicarbonate  with  100 
ml  of  distilled  water  until  solution  has  been  effected.  Then  add 
enough  distilled  water  to  make  the  solution,  when  cold,  meas- 
ure 970  ml,  and,  lastly,  add  the  compound  spirit  of  lavender. 
Filter  through  paper. 

Reaction.     As2O3+4KHCO3=2K2HAsO3H-  H2O+4CO2. 

Notes.  Prior  to  the  revision  of  1890  the  Pharmacopoeia  of  the 
United  States  contained  a  working  formula  for  this  preparation 
which  called  for  only  one-half  as  much  potassium  bicarbonate 
as  is  necessary.  The  proportions  were,  in  other  words,  equal 
parts  of  arsenous  oxide  and  potassium  bicarbonate.  The  com- 
plaints frequently  made  that  arsenic  separated  from  Fowler's  so- 
lution on  standing  may  have  been  due  to  that  error.  If  12  Gm  of 
KOH  be  used  instead  of  the  26  Gm  of  KHCO3  the  arsenous 
oxide  dissolves  much  more  rapidly  and  the  final  result  is  the 
same.  It  is  necessary  that  the  compound  tincture  of  lavender 
be  added  last  in  order  to  obtain  a  clear  solution. 

Description. — A  clear  liquid,  having  a  reddish  color  and  an 


POTASSIUM    BENZOATE. 


527 


aromatic  odor  derived  from  the  compound  tincture  of  lavender. 
It  has  an  alkaline  reaction  on  litmus  paper. 

POTASSIUM    BENZOATE. 

POTASSII    BENZOAS. 

KC7H.O2.3H2O=2i4. 

Potassium   bicarbonate 82  parts 

Benzoic   acid 100  parts 

Distilled   water 500  parts 

Dissolve,  neutralize,  filter  and  evaporate  to  dryness,  or  to  crys- 
tallization. 

White,  odorless,  or  of  faint  benzoin  odor;  sweetish;  readily 
soluble. 

POTASSIUM    BICARBONATE. 

POTASSII    BICARBONAS. 
KHCO3:=IOO. 

Prepared  by  treating  potassium  carbonate  with  carbonic  acid 
gas.  The  gas  is  either  conducted  into  a  concentrated  solution 
of  the  carbonate,  or  over  the  moist  salt.  To  facilitate  the  absorp- 
tion of  carbonic  acid  the  potash  is  mixed  with  powdered  charcoal. 
The  moist  mass  is  exposed  to  the  action  of  the  carbonic  acid  gas 
until  a  test  portion  in  solution  no  longer  precipitates  a  solution 
of  magnesium  sulphate. 

The  black  mass  is  mixed  with  \v£ter,  heated  to  about  70°  or 
80°  C,  the  solution  is  filtered  while  warm  to  remove  the  charcoal 
and  the  silica  which  has  been  precipitated  by  the  carbonic  acid, 
and  the  filtrate  is  set  aside  in  a  cool  place  to  crystallize.  The  crys- 
tals are  carefully  washed  to  remove  adhering  mother  liquor,  which 
contains  normal  carbonate,  a  little  bicarbonate,  chloride,  and  sul- 
phate of  potassium. 

Description. — A  white  salt,  crystalline,  and  soluble  in  3.2  parts 
of  water.  Insoluble  in  alcohol.  When  absolutely  pure  the  reac- 
tion is  neutral  or  only  very  slightly  alkaline.  By  heat  it  is  con- 
verted into  the  monocarbonate  with  loss  of  CO2.  Dissolved  in 


POTASSIUM  BICARBONATE. 


water  it  loses  carbonic  acid  even  at  ordinary  temperatures,  but 
rapidly  and  to  complete  conversion  into  normal  carbonate  above 
50°  C.  In  the  dry  state  it  does  not  readily  part  with  any  of  its 
carbonic  acid  until  at  100°  C. 


POTASSIUM    BITARTRATE. 

POTASSII    BITARTRAS. 

KHC4H406=i88. 

In  the  manufacture  of  wine  a  large  amount  of  impure  potassium 
bitartrate  is  deposited  from  the  grape  juice  during  the  second 
fermentation,  the  salt  being  thrown  out  of  solution  by  the  alcohol 
formed.  Thick  crusts  are  formed  in  the  vats,  over  the  bottom 
and  sides.  The  bitartrate  formed  on  the  bottom  contains  more 
calcium  salt  than  that  on  the  sides.  The  "argols"  or  "crude  tar- 
tar" must  be  powdered,  redissolved  in  boiling  water,  freed  from 
coloring  matter  by  the  addition  of  clay,  which  carries  it  down 
in  settling.  The  solution  is  then  clarified  with  albumen,  strained, 
and  allowed  to  deposit  crystals.  The  crystals  forming  on  the 
sides  are  again  less  impure  than  those  on  the  bottom.  Their  rela- 
tive freedom  from  calcium  salt  is  indicated  by  their  clearness  or 
opacity,  the  milky  opaque  crystals  being  more  contaminated  with 
calcium  tartrate. 

This  purified  argols  or  refined  tartar  is  further  purified  by  re- 
ducing it  to  fine  powder  and  digesting  this  with  pure  hydrochloric 
acid  diluted  with  distilled  water.  The  calcium  tartrate  is  then 
decomposed  by  the  hydrochloric  acid,  forming  calcium  chloride 
and  free  tartaric  acid,  both  of  which  are  washed  out.  The  mix- 
ture is  now  allowed  to  cool,  so  that  most  of  the  potassium  bitar- 
trate dissolved  in  the  water  may  deposit  again,  after  which  the 
"cream  of  tartar"  is  washed  with  cold  water  until  the  washings 
cease  to  give  any  reaction  for  chlorides,  and  then  dried.  A  small 
percentage  of  bitartrate  is  lost  by  solution  in  the  water  with  which 
it  is  treated. 

Description. — Colorless  or  slightly  opaque  crystals  or  a  white 
powder  having  no  odor,  but  an  agreeable  acidulous  taste. 
Soluble  in  201  parts  of  water  at  15° ;  but  in  16.7  parts  of  boiling 
water. 


BORAX  TARTAR. 

BORAX  TARTAR. 

TARTARUS    BORAXATUS. 

[Boro-Tartrate  of  Potassium  and  Sodium.] 

Borax,  in  powder 2  parts 

Potassium  bitartrate 5  parts 

Boiling   water 20  parts 

Put  the  salts  in  the  water,  contained  in  a  porcelain  dish,  and 
stir  until  all  is  dissolved.  Filter.  Evaporate  the  solution  until 
a  thread  of  the  semi-liquid  residue  becomes  brittle  on  cooling. 
Then  pull  it  into  sticks,  or  flatten  it  out  in  thin  cakes,  and  dry 
it  by  the  aid  of  heat.  Powder  the  product  in  a  warm  mortar, 
and  keep  it  in  tightly  closed  bottles. 

Notes.  In  some  pharmacopoeias  tlie  proportions  are  I  part  of 
borax  to  2  parts  of  cream  of  tartar.  There  is  undoubtedly  a 
chemical  union  of  some  kind  between  the  two  salts,  but  the  prod- 
uct is  not  a  definite  chemical  compound.  However,  when  i  part 
of  borax  and  3  parts  of  potassium  bitartrate  are  combined,  a 
double  salt  is  formed  having  the  composition  (according  to 
Duve)  : 

KNaC4Hs(BO)06+KHC4H3(BO)06. 

It  is  sometimes  directed  that  the  cream  of  tartar  should  be 
added  gradually  to  the  borax  previously  dissolved  in  the  water. 
This  it  not  only  unnecessary,  but  delays  the  operation  consider- 
ably. If  both  salts  are  added  at  once  the  solution  of  both  is  far 
more  rapid  than  the  solution  of  borax  alone  would  be.  Constant 
stirring  is,  however,  necessary,  because  otherwise  the  borax  on 
the  bottom  of  the  dish  ca^es  together  and  afterwards  dissolves 
rather  slowly. 

When  large  amounts  are  operated  upon,  water-bath  heat  is  in- 
sufficient for  evaporating  the  solution  to  dryness ;  steam-heat  and 
constant  stirring  must  be  employed.  Having  evaporated  the  so- 
lution to  dryness  we  have  a  yellowish  gummy  residue,  which  on 
cooling  has  a  glassy  fracture.  This  is  then  dried  in  thin  cakes 
or  threads  at  70°  C. ;  it  is  sufficiently  dry  when  white  and  porous. 

Vol.   11—34 


530  BORAX  TARTAR. 

To  powder  the  product  fine  is  both  difficult  and  disadvantage- 
ous ;  it  should  only  be  reduced  to  a  very  coarse  powder,  in  a  warm 
mortar,  and  then  at  once  put  into  warm,  dry  bottles  which  must  be 
tightly  corked. 

Description.— A  coarse,  white  powder,  dry,  very  deliquescent, 
soluble  in  its  own  weight  of  cold  water,  but  insoluble  in  alcohol. 
It  has  a  pleasant  acidulous  taste. 

Potassium  Boro-Tartrate. 

Potassium  bitartrate 4  parts 

Boric  acid i  part 

Boiling   water 10  parts 

Heat  together  with  constant  stirring  until  dissolved.     Filter, 
and  evaporate  to  dryness. 
Powder  the  residue. 

Description. — A  white  powder  having  an  agreeable  acidulous 
taste.  It  is  not  deliquescent.  Soluble  in  twice  its  weight  of 
water ;  insoluble  in  alcohol. 


POTASSIUM    BROMATE. 

POTASSII    BROMAS. 

KBrO3— 167. 

Bromine  87  parts 

Potassium   hydroxide 61  parts 

Water    100  parts 

Dissolve  the  potassium  hydroxide  in  the  water  in  a  half-liter 
flask.  Add  the  bromine  very  gradually,  keeping  the  flask  in  cold 
water  and  shaking  well  after  each  addition  of  bromine.  The 
solution,  after  all  of  the  bromine  has  been  added,  should  be  neutral 
and  colorless.  If  yellow  or  red  add  more  potassium  hydroxide 
until  slightly  alkaline  and  let  stand  until  colorless,  after  which 
neutralize  carefully  with  hydrobromic  acid.  Filter  the  liquid 
and  set  it  aside  in  a  cold  place  for  some  hours.  Collect  the  crys- 
tals of  bromate  which  have  separated,  drain  them  well.  Redis- 
solve  the  salt  in  three  times  its  weight  of  boiling  distilled  water, 


POTASS  I  U  M     r-R(  ).M  ATE.  53 1 

filter  the  solution,  and  set  it  in  a  cool  place.     When  cold,  put  it 
in  an  ice-water  bath.     Collect,  drain  and  dry  the  crystals. 

The  residuary  solutions  contain  potassium  bromide  which 
should  be  recovered  in  the  usual  way. 

Reaction.     6KOH+3Br2==sKBr+KBrO3+3H2O. 

Description. — White  or  colorless  crystals.  Odorless.  Taste 
saline.  Soluble  in  14  parts  of  water  at  20° ;  in  about  3  parts  at 
80°,  and  in  about  2  parts  of  boiling  water. 


POTASSIUM    BROMIDE. 

POTASSII    BROMIDUM. 


Iron  wire,  cut  .................  '  .......  5  parts 

Bromine  .............................  12  parts 

Potassium   bicarbonate  ...............  .,  15  parts 

Distilled  water. 

Put  the  iron  together  with  40  parts  of  distilled  water  in  a  flask. 
Add  9  parts  of  bromine,  in  small  portions  at  a  time,  shaking  the 
flask  after  each  addition.  Heat  the  flask  and  contents  if  neces- 
sary to  cause  the  reaction  to  be  completed  —  i.  e.,  until  all  odor 
of  bromine  ceases  and  a  green  solution  of  ferrous  bromide  results. 
Filter,  the  solution.  Add  the  remainder  of  the  bromine  to  the 
filtrate  and  shake  well. 

Put  the  potassium  bicarbonate  in  a  porcelain  dish  with  50  parts 
of  distilled  water,  heat  until  effervescence  ceases,  and  then  raise 
the  heat  to  boiling. 

Add  slowly  to  the  boiling  solution  of  potassium  carbonate  the 
solution  of  bromide  of  iron.  Boil  the  mixture  for  fifteen  min- 
utes. .The  solution  should  now  have  a  slightly  alkaline  reaction. 
If  not,  add  more  potassium  carbonate  or  bicarbonate  until  the 
reaction  is  alkaline. 

Let  the  precipitate  subside.  Filter  the  solution.  Wash  the 
precipitate  on  the.  filter  with  hot  distilled  water  and  add  the  wash- 
ings to  the  filtrate.  Evaporate  the  solution  to  the  requisite  degree 
of  concentration  and  set  it  aside  to  crystallize.  Drain  the  crys- 


532  POTASSIUM    BROMIDE. 

tals  in  a  funnel.  Then  spread  the  salt  upon  bibulous  paper  and 
dry  it  with  the  aid  of  moderate  heat. 

Additional  crystals  may  be  obtained  from  the  mother-liquor  in 
the  usual  way. 

Instead  of  crystallizing  the  salt  the  solution  may  be  evaporated 
to  dryness  and  the  bromide  granulated. 

Reaction. 

Fe+2Br=FeBr2 ;  then  3FeBr2+Br2=FeBr2.2FeBr3; 
and,  finally,  FeBr2.2FeBr3+4K2CO3 
=8KBr+FeO.Fe2O3+4CO2. 

Notes.  Ferroso-ferric  bromide  gives  better  results  than  fer- 
rous bromide  because  the  iron  is  more  readily  and  completely  pre- 
cipitated in  the  form  of  ferroso-feric  oxide. 

Potassium  bromide  crystallizes  best  from  a  slightly  alkaline 
solution.  But  if  the  salt  is  to  be  recovered  in  a  granular  condi- 
tion by  evaporation  to  dryness  with  constant  stirring,  then  the 
solution  should  be  neutral.  It  is,  however,  necessary  to  render 
the  solution  faintly  alkaline  for  the  purpose  of  precipitating  all 
the  iron.  The  liquid  can  afterwards  be  made  neutral  again  by 
adding  enough  hydrobromic  acid,  which,  for  this  purpose,  may 
well  be  made  from  potassium  bromide  and  tartaric  acid. 

To  improve  the  appearance  of  potassium  bromide  the  crystals 
may,  after  drying,  be  heated  for  a  few  minutes  at  a  temperature 
of  80°  to  100°. 

Second  Method. 

Solution  of  potassium  hydroxide 250  parts 

Bromine,    about 20  parts 

Wood  charcoal,  in  fine  powder 10  parts 

Boiling  distilled  water 150  parts 

Put  the  solution  of  hydroxide  in  a  flask;  add  the  bromine 
gradually,  writh  constant  agitation,  until  the  liquid  has  acquired 
a  permanently  brown  color.  Evaporate  to  dryness ;  powder  the 
residue  and  mix  it  well  with  the  charcoal.  Throw  the  mixture 
into  a  red  hot  iron  crucible,  and  when  reduced  to  a  state  of  fusion, 
pour  out  the  contents,  let  cool,  dissolve  it  in  the  boiling  water, 


POTASSIUM    BROMIDE.  533 

filter,  and  set  aside  to  crystallize.  Drain  the  crystals  and  dry 
them  in  a  warm  place.  Recover  the  salt  contained  in  the  mother 
liquor  by  evaporation  to  dryness,  stirring  constantly. 

Reaction. 

3Br2+6KOH=5KBr+KBrO3+3H2O ;  and  then, 
2KBrO3+3Cr=2KBr+3CO2. 

Notes.  A  stronger  solution  of  potassium  hydroxide  than  the 
official  "liquor  potassse"  (5%)  may  well  be  used.  In  that  case 
the  reaction  must  be  controlled  to  prevent  the  liquid  from  be- 
coming too  hot ;  this  may  be  accomplished  by  keeping  the  flask 
in  cold  water  while  the  bromine  is  being  very  slowly  added.  See 
also  notes  under  Potassium  Iodide. 

Third  Method. 

Ammonium   bromide 98  parts 

Potassium   bicarbonate 100  parts 

Dissolve  the  ammonium  bromide  in  100  parts  of  hot  water; 
add  the  potassium  bicarbonate ;  boil  the  solution  until  all  odor  of 
ammonia  has  ceased.  Then  crystallize  the  potassium  bromide. 

Description. — Colorless  or  white  cubical  crystals,  or  a  white 
granular  salt;  odorless,  and  of  saline,  pungent  taste.  Soluble  at 
15°  in  about  1.6  parts  of  water  and  in  200  parts  of  alcohol;  in 
less  than  its  own  weight  of  boiling  water,  and  in  16  parts  of 
boiling  alcohol.  Soluble  in  four  times  its  weight  of  glycerin. 
The  water-solution  must  have  a  neutral  reaction  on  test-paper, 
or  only  a  very  faintly  alkaline  reaction. 


POTASSIUM    CARBONATE. 

POTASSII    CARBON  AS. 

[Potash.     Pearl- Ash.     Salts  of  Tartar.] 
K2C03=i38. 

Potassium  carbonate  is  contained  in  wood  ashes,  and  may  be 
washed  out  of  the  ashes  by  lixiviation,  the  salt  being  recovered 


534  POTASSIUM    CARBONATE. 

from  the  solution  by  boiling  it  down  to  dryness.  The  residue  is 
then  purified  by  heating  it  strongly  in  a  furnace  until  all  organic 
matters  have  been  destroyed.  Calcined  potash  is  the  result;  it 
contains  50  to  80  per  cent  of  potassium  carbonate,  and  is  con- 
taminated with  sulphate,  chloride,  etc.  By  converting  this  crude 
potassium  carbonate  into  bicarbonate,  most  of  the  impurities  are 
removed,  and  a  nearly  pure  normal  carbonate  can  then  be  pre- 
pared from  the  bicarbonate. 

Formerly,  pure  potassium  carbonate  was  prepared  by  strongly 
heating  (detonating)  potassium  bitartrate  with  half  its  weight  of 
potassium  nitrate. 

At  Stassfurth,  potassium  carbonate  is  prepared  as  follows : 
A  solution  of  magnesium  sulphate  (kieserite)  is  mixed  with  a 
solution  of  crude  potassium  chloride,  both  of  the  materials  being 
taken  from  the  Stassfurth  mines ;  a  double  salt  of  sulphate  of  po- 
tassium and  magnesium  is  then'  formed  together  with  a  double 
chloride  (carnallite)  :  3KCl+2MgSO4=K2Mg(SO4)2+KMgCl3. 
The  double  sulphate  is  boiled  with  more  potassium  chloride,  which 
results  in  the  formation  of  potassium  sulphate  and  carnallite.  The 
carnallite  decomposes  slowly  in  water  so  that  the  magnesium 
chloride  can  be  separated,  and  the  potassium  chloride  is  then 
used  over  again  as  before — 

K2Mg(SO4)2+3KCl=2K2SO,+KCl+MgCl2. 

The  potassium  sulphate  is  then  turned  into  carbonate  by  a  process 
analogous  to  Leblanc's  method  for  manufacturing  soda.  The 
resulting  product  contains  92  to  93  per  cent  of  potassium  car- 
bonate, 2  or  3  per  cent  of  sodium  carbonate,  2  per  cent  of  potas- 
sium chloride,  and  i  to  2  per  cent  of  potassium  sulphate. 

Crude  potash  may  be  partly  purified  by  dissolving  it  in  twice 
its  weight  of  water,  letting  it  stand  two  days,  decanting,  filtering 
through  linen,  and  evaporating  the  clear  liquid  in  a  clean  iron 
vessel  until  a  pellicle  begins  to  form  on  the  surface.  The  liquid 
is  then  put  in  a  stone  pot  and  set  aside  for  a  week,  in  order  that 
sulphates,  chlorides,  etc.,  may  crystallize  out.  The  solution  is 
then  filtered  and  boiled  down  to  dryness  in  an  iron  pot,  stirring 
constantly  at  the  close  so  as  to  obtain  a  dry,  granular  product. 

Pure  potassium  carbonate  for  pharmaceutical  and  medicinal 
uses  is  most  readily  obtained  by  heating  potassium  bicarbonate 


POTASSIUM    CARBONATE.  535 

until  the  residue  is  entirely  soluble  in  twice  its  weight  of  water, 
or  until  it  has  lost  from  30  to  31  per  cent  of  its  weight. 

Being  very  deliquescent,  potassium  carbonate  must  be  kept  in 
tightly  closed  vessels. 

Preparation  of  Potassium  Carbonate  from  Bicarbonate 

Potassium  bicarbonate,   any   desired   quantity. 

Put  the  salt  into  a  porcelain  dish,  cover  it  well  with  distilled 
water,  heat  gradually  and  continue  the  heat  until  effervescence 
ceases  and  the  liquid  boils.  Then  evaporate  to  dryness,  stirring 
constantly.  Put  the  product  at  once  into  a  perfectly  dry  bottle 
and  close  this  tightly. 

Reaction.     2KHCO3=K2CO3+H2O+CO2. 

Notes.  To  obtain  a  perfect  product  the  potassium  bicarbonate 
used  must  be  perfectly  clean  and  pure.  If  it  makes  an  unclear 
solution  in  water,  the  bicarbonate  should  all  be  dissolved  in  about 
five  or  six  times  its  weight  of  water  and  the  solution  filtered 
before  it  is  heated  to  decompose  it  into  normal  carbonate,  water 
and  carbon  dioxide. 

The  product  must  be  perfectly  dry  and  white. 

Description. — Potassium  carbonate,  sufficiently  pure  to  fulfill 
the  requirements  of  the  Pharmacopoeia,  is  a  white  granular 
powder,  odorless,  of  strongly  alkaline  taste.  It  is  very  deliques- 
cent. Soluble  in  i.i  parts  of  water  at  15°,  and  in  0.65  part  of 
boiling  water.  Insoluble  in  alcohol. 

POTASSIUM    CHLORATE. 

POTASSII    CHLORAS. 

KC1O3= 122.4. 

Formerly  prepared  by  saturating  a  solution  of  potassium  hy- 
droxide or  carbonate  with  chlorine,  whereby  hypochlorite  and 
chloride  of  potassium  were  formed,  the  hypochlorite  being  after- 
wards decomposed  by  heat  into  chloride  and  chlorate : 

2KOH+C12=KC1O+KC1+H2O ;  and  then, 
3KC10=KC103+2KC1. 


53^  POTASSIUM   CHLORATE. 

The  -chlorate  being  much  less  soluble  than  the  chloride  is 
readily  separated  by  crystallization  from  the  solution. 

Liebig's  method,  now  used,  consists  in  treating  a  mixture  of 
calcium  hydroxide  and  potassium  chloride  with  chlorine,  when 
calcium  chlorate  is  formed.  Then  the  calcium  chlorate  and  potas- 
sium chloride  interact  to  form  potassium  chlorate  and  calcium 
chloride.  The  product  is  readily  crystallized  out  from  the  liquid 
and  purified  by  recrystallization. 

Turbidated  Potassium  Chlorate. 
KC1O3=  122.4. 

Potassium  chlorate i  part 

Boiling  distilled  water 5  parts 

Dissolve  and  filter.  Stir  the  filtrate  constantly  until  cold.  Col- 
lect the  crystals  on  a  filter,  let  drain,  and  then  dry  the  product. 

Notes.  Commercial  potassium  chlorate  usually  contains  po- 
tassium chloride  and  calcium  chloride.  These  impurities  are 
much  more  readily  water-soluble  than  potassium  chlorate.  Hence 
the  turbidation  of  the  salt  results  also  in  purification,  for  the 
chlorides  remain  in  the  mother  liquor. 

When  cooled  to  15°  C.  the  mother  liquor  still  retains  about 
6  per  cent  of  its  weight  of  chlorate,  or  30  per  cent  of  the  amount 
of  salt  operated  upon.  This  must  be  recovered  as  far  as  prac- 
ticable, which  can  be  effected  by  evaporating  the  mother-liquor 
by  water-bath  heat  to  about  one-third  its  bulk,  stirring  until  cold, 
and  collecting,  draining  and  drying  the  "second  crop"  of  small 
crystals  in  the  same  manner  as  the  first. 

Description. — Potassium  chlorate  consists  of  colorless  crystals, 
or  'a  glistening,  white,  crystalline  powder,  odorless,  of  a  cooling 
saline  taste.  Soluble  in  16.7  parts  of  water  at  15°;  in  about  3 
parts  of  water  at  75°,  and  in  1.7  parts  of  boiling  water.  Nearly 
insoluble  in  alcohol.  Explosive  with  certain  readily  oxidized  sub- 
stances, especially  when  heated  with  them,  or  mixed  with  reduc- 
ing agents  by  trituration,  or  by  concussion.  A  powerful  oxidiz- 
ing agent. 


POTASSIUM    CHLORIDE.  537 

POTASSIUM    CHLORIDE. 

POTASSII    CHLORIDUM. 

KC1=74.4. 

Potassium  bicarbonate 100  parts 

Diluted  hydrochloric  acid / .  .   364  parts 

Distilled   water 100  parts 

Heat  the  potassium  bicarbonate  in  a  porcelain  dish  with  the 
water  until  converted  into  normal  carbonate.  Then  add  this 
gradually  to  the  hydrochloric  acid,  stirring  well.  When  the  so- 
lution is  neutral  to  test-paper,  filter  it,  and  evaporate  the  filtrate 
to  crystallization  or  granulation,  as  may  be  desired. 

Reaction.     K2CO3+2HC1=2KC1+H2O+CO2. 

Purification  of  crude  potassium  chloride.  The  commercial 
crude  salt  contains  sulphates  and  chlorides  of  magnesium,  sodium 
and  calcium.  It  is  purified  as  follows: 

Crude   chloride 2  parts 

Water 5  parts 

Dissolve  the  salt  in  the  water  with  the  aid  of  heat  (about  80°). 
Add  about  0.05  part  of  lime  previously  slaked  and  mixed  with 
ten  times  its  weight  of  water  to  precipitate  magnesium.  Stir 
well.  Filter.  Add  to  the  filtrate  enough  solution  of  barium 
chloride  to  precipitate  the  sulphates.  Filter  again.  Then  add 
enough  solution  of  ammonium  carbonate  to  precipitate  the  calcium 
and  barium.  Filter  a  third  time.  Evaporate  the  filtrate  to  dry- 
ness  and  heat  the  residue  at  a  low  red  heat  to  decompose  the 
ammonium  salt.  Dissolve  the  mass  in  water,  acidulate  the  solu- 
tion with  hydrochloric  acid,  boil  the  liquid  a  few  minutes,  filter, 
and  evaporate  to  the  density  of  1.20.  Set  aside  to  crystallize. 
Drain  and  dry  the  crystals. 

Description. — Colorless  translucent  crystals,  or  a  white  granular 
salt;  odorless  and  of  a  pure  saline  taste.  Soluble  at  15°  in  about 
three  times  its  weight  of  water,  and  in  less  than  one-half  its 
weight  of  boiling  water.  Insoluble  in  alcohol. 


53$  POTASSIUM   CITRATE. 

POTASSIUM    CITRATE. 

POTASSII    CITRAS. 

K3C6H507.H20= 324. 

Potassium   bicarbonate 10  parts 

Citric  acid. .  .  ^ 7  parts 

Crush  the  citric  acid  and  the  bicarbonate,  separately ;  add  the 
latter  gradually  to  50  parts  of  boiling  water,  and  when  efferves- 
cence ceases  add  the  citric  acid,  a  small  portion  at  a  time,  until 
the  liquid  is  neutral  to  litmus  paper,  or  but  faintly  alkaline.  Fil- 
ter, and  evaporate  to  dryness,  stirring  constantly  after  a  pellicle 
has  commenced  to  form,  so  that  the  product  may  be  granular. 

Reaction. 

H3C6H5O7+3KHCO3=:K3C6H5O7.H2O+3CO2+2H2O; 

or,  2HSC6H5O7+3K2CO8=2KSC6H5O7+3CO2+3HA 

Notes.  The  temperature  must  not  be  too  high  toward  the  close 
of  the  evaporation,  as  citric  acid  and  citrates  are  decomposed  at  a 
high  heat. 

The  product  should  be  perfectly  white,  and  must  be  entirely 
dry  before  it  is  bottled. 

Description. — White,  transparent  crystals,  or  a  white  granular 
powder;  odorless,  and  of  a  pure  saline,  cooling  taste.  Hygro- 
scopic. Soluble  in  0.6  part  of  water  at  15°,  and  freely  soluble  in 
boiling  water.  Sparingly  soluble  in  alcohol.  Neutral  to  litmus 
paper. 

Potassium  Citrate  Solution. 

LIQUOR    POTASSII    CITRATIS. 

Citric  acid 6  parts 

Potassium   bicarbonate 8  parts 

Dissolve  each  in  40  parts  of  cold  water.  Filter  the  solutions 
separately,  and  wash  the  niters  with  enough  water  to  obtain,  in 
each  case,  50  parts  of  filtrate.  Mix  the  two  solutions,  and,  when 


POTASSIUM   CITRATE.  539 

effervescence  has  nearly  ceased,  put  the  product  in  a  bottle  and 
cork  it  tightly. 

Should  be  freshly  prepared  whenever  required  for  use. 

Notes.  It  is  intended  that  cold  water  should  be  used,  and  that 
the  preparation  should  retain  in  solution  as  much  of  the  carbonic 
acid  as  may  be  soluble  in  that  volume  of  the  watery  liquid.  An 
excess  of  citric  acid  is  purposely  employed  in  order  that  the 
preparation  may  have  a  slightly  acidulous  taste. 

Description. — A  clear,  colorless,  liquid,  of  pure  mildly  saline 
taste  and  slightly  acid  reaction. 

Effervescent  Potassium  Citrate. 

Citric   acid 63  Gm 

Potassium    bicarbonate 90  Gm 

Sugar 47  Gm 

Powder  the  ingredients  separately,  and  mix  them  thoroughly 
in  a  warm  mortar.  Dry  the  resulting,  uniform  paste  rapidly  at 
a  temperature  not  exceeding  120°  C.,  and,  when  it  is  perfectly  dry, 
reduce  it  to  a  powder  of  the  desired  degree  of  fineness. 

Keep  the  product  in  well-stoppered  bottles. 

Notes.  A  partial  reaction  ensues  when  the  ingredients  are  trit- 
urated together  in  a  warm  (not  hot)  mortar,  on  account  of  the 
water  always  contained  in  the  citric  acid,  and  the  liberation  of  a 
portion  of  water  formed  by  the  reaction  renders  the  mixture  some- 
what pasty  at  the  moderate  heat  employed.  When  the  mixture 
is  dissolved  in  water  a  complete  reaction  takes  place  and  normal 
potassium  citrate  is  formed : 

3KHCO,+H,C.H.OT.H,0=K,C.HA-H,0+3HS0+3CX>1. 

Potassium  Boro-Citrate. 

Citric  acid 10  Gm 

Boric  acid 9  Gm 

Potassium  carbonate 15  Gm 

Water  60  ml 

Dissolve  and  evaporate  to  dryness,  stirring  constantly. 

Description. — A  perfectly  white  salt,  readily  forming  a  clear 
solution  in  water. 


54°  POTASSIUM   CYANATE. 

POTASSIUM    CYANATE. 

POTASSII    CYANAS. 

KCNO=8i. 

Anhydrous  potassium  f errocyanide 4  parts 

Dry  potassium  dichromate 3  parts 

Alcohol    18  parts 

Methyl  alcohol 2  parts 

Melt  the  potassium  dichromate,  and,  while  it  is  still  warm, 
mix  it  with  the  powdered  anhydrous  potassium  ferrocyanide. 
Put  the  mixture,  a  small  spoonful  at  a  time,  into  a  large  iron  dish 
heated  over  a  gas  stove,  stirring  with  an  iron  spatula  after  each 
addition  so  that  each  portion  of  powder  added  is  converted  into 
a  black  mass,  taking  care  not  to  raise  the  temperature  so  high  that 
the  mass  fuses. 

Powder  the  black  mass  while  still  warm.  Then  put  it  in  a  flask 
and  heat  it  in  a  water-bath  for  ten  minutes  with  a  mixture  of  the 
two  alcohols,  shaking  the  contents  frequently  and  well. 

Decant  the  clear  solution  through  a  pleated  filter  into  a  beaker 
placed  in  crushed  ice. 

Set  the  flask  containing  the  undissolved  black  residue  in  ice 
water  without  delay. 

After  the  crystals  have  deposited  in  the  beaker,  pour  the  mother 
liquor  back  over  the  black  mass  in  the  flask. 

Repeat  the  extractions  of  the  cyanate  from  the  residue  if  nec- 
essary. 

Drain  the  crystals,  wash  them  with  strong  ether  and  dry  them 
in  vacua  over  sulphuric  acid. 

Notes.  To  make  anhydrous  potassium  ferrocyanide,  heat  the 
crushed  commercial  salt  in  an  iron  dish  slowly  until  completely 
effloresced,  or  until  no  yellow  unchanged  salt  remains  in  the  in- 
terior of  any  piece.  Then  powder  it  while  still  warm  and  com- 
plete the  drying  by  heating  the  powder  spread  out  in  a  thin  layer 
on  a  hot  iron  plate  or  dish  for  two  or  three  hours. 

When  the  mixed  salts  are  heated  to  a  black  mass  there  should 
be  no  evolution  of  ammonia  and  there  will  be  none  if  the  materials 
were  first  thoroughly  dried. 

The  yield  is  about  1.7  parts.  The  product  is  very  unstable. 
Decomposed  by  water. 


POTASSIUM    CYANIDE.  54! 

POTASSIUM    CYANIDE. 

POTASSII    CYANIDUM. 

KCy=65. 

Potassium    ferrocyanide,    dried    and    pow- 
dered       8  parts 

Potassium  carbonate,  dry 3  parts 

Mix  the  powdered  materials  well,  throw  the  mixture  into  a  deep 
iron  crucible  previously  heated  to  dull  redness,  and  maintain  the 
heat  until  effervescence  ceases  and  the  fused  mass  solidifies  on 
cooling,  which  may  be  ascertained  by  dipping  a  warm  glass  rod 
in  it  and  withdrawing.  When  the  fused  cyanide  assumes  a  pure 
white  color  on  cooling,  pour  it  out  into  a  shallow  dish,  and,  when 
solid,  break  it  into  pieces  and  put  it  in  dry  bottles  while  still  warm. 

Reaction.     K4FeCy6+K2CO3=5KCy+KOCy+CO2+Fe. 

Notes.  Care  is  to  be  taken  to  decant  the  fused  cyanide  prop- 
erly from  the  residue — that  is,  the  pouring  must  be  discontinued 
as  soon  as  the  decanted  fused  salt  is  no  longer  white. 

The, product  contains  cyanate  as  well  as  cyanide. 

Another  process  consists  in  conducting  hydrocyanic  acid  into 
solution  of  potassa  to  which  alcohol  has  been  added.  The  cyanide 
formed  is  then  deposited  in  small  crystals,  which  are  to  be  drained 
on  a  funnel,  washed  with  strong  alcohol,  in  which  the  preparation 
is  nearly  insoluble,  and  dried  between  bibulous  paper  at  a  moderate 
heat. 

Being  deliquescent,  and  readily  absorbing  carbonic  acid  from 
the  air  with  the  formation  and  loss  of  hydrocyanic  acid,  the  prod- 
uct must  be  kept  in  tightly  closed  bottles. 

Description. — White,  amorphous  pieces,  or  a  white,  granular 
powder,  odorless  when  dry,  but  in  moist  air  emitting  the  odor  of 
hydrocyanic  acid.  The  taste  is  sharp,  and  somewhat  alkaline. 

Deliquescent  in  moist  air.     Very  poisonous. 

Soluble  in  about  2  parts  of  water  at  15°  C.  Boiling  water 
dissolves  its  own  weight  of  the  salt,  but  rapidly  decomposes  it. 
In  alcohol  it  is  but  sparingly  soluble. 


542  POTASSIUM  BICHROMATE. 

POTASSIUM    BICHROMATE. 

POTASSII    DICHROMAS. 

K2Cr207=294. 
[Potassium  Bichromate.] 

Chromite,  in  powder 6  parts 

Potassium   carbonate 3  parts 

Lime 8  parts 

Potassium   sulphate I  part 

Sulphuric  acid. 
Water. 

Dissolve  the  potassium  carbonate  in  3  parts  of  water. 

Slake  the  lime  in  a  large  porcelain  dish  with  about  two-thirds 
of  the  solution  of  potassium  carbonate.  Then  add  the  remainder 
of  that  solution  and  mix  the  whole  well.  Evaporate  the  mixture 
to  dryness.  Heat  the  residue  to  150°  and  stir  it  until  reduced  to 
powder.  Mix  this  with  the  powdered  chromite. 

Heat  the  dry  mixture  to  a  bright  red  heat  for  three  or  four 
hours  in  free  contact  with  air,  stirring  frequently. 

Let  the  mass  cool,  powder  it,  and  mix  the  powder  with  20 
parts  of  water,  stirring  well.  Strain  the  solution  and  evaporate 
the  colature  until  crystals  begin  to  form. 

Dissolve  the  potassium  sulphate  in  I  part  of  boiling  water,  and 
add  this  solution  gradually  to  the  concentrated  solution  of  chro- 
mate,  so  long  as  precipitation  of  calcium  sulphate  is  produced 
by  it.  Then  filter  while  hot. 

To  the  hot  yellow  filtrate  add  sulphuric  acid  diluted  with  twice 
its  volume  of  water  until  the  liquid  is  strongly  acid.  Let  the 
liquid  cool.  Collect  the  crystalline  precipitate  on  an  asbestos  or 
glass  wool  filter,  or  on  a  bed  of  broken  glass  in  a  funnel.  Purify 
the  salt  by  recrystallization. 

Drain  the  crystals  of  dichromate  and  dry  them  with  the  aid 
of  moderate  heat. 

Reaction.     4Cr2FeO4+8K2CO3+7O2=8K2CrO4+2Fe2O3+ 
8CO2;    and    4Cr2FeO4+8Ca(OH)2+7O2=8CaCrO4+2Fe2O3+ 
8H2O;    then    CaCrO4+K2SO4=K2CrO4+CaSO4 ;    and,    finally, 
2K2CrO4+H2SO4==K2Cr2O7H-K2SO4+H2O. 


POTASSIUM  DICHROMATE.  543 

Notes.  The  chromite  consists  mainly  of  Cr2FeO4  but  also  con- 
tains silicates.  When  ignited  with  the  potash  and  lime  it  forms 
ferric  oxide,  the  chromates  of  potassium  and  calcium,  and  potas- 
sium silicate.  The  ignition  may  be  performed  in  a  muffle  furnace, 
or,  more  advantageously,  in  a  reverbatory  furnace,  using  the 
oxidation  flame. 

The  lime  is  used  in  large  excess  to  keep  the  mass  porous  when 
ignited,  and  a  portion  of  it  forms  chromate  so  that  the  amount 
of  potassium  carbonate  required  is  lessened.  The  chromates  are 
leeched  out  of  the  mass  with  water,  and  the  potassium  sulphate 
is  added  to  convert  the  calcium  chromate  into  potassium  chromate, 
calcium  sulphate  being  precipitated.  The  liquid  containing  the 
chromates  is  yellow. 

When  sulphuric  acid  is  added  to  the  solution  of  potassium 
chromate  the  color  of  the  liquid  is  at  once  changed  from  yellow 
to  orange  red,  and,  as  the  potassium  dichromate  now  formed 
is  much  less  soluble  in  water  than  the  chromate,  a  large  propor- 
tion of  the  dichromate  crystallizes  out  on  cooling.  The  quantity 
of  water  prescribed  is  adjusted  with  this  view. 

The  first  crop  thus  obtained  is  nearly  free  from  potassium 
sulphate  and  may  be  purified  by  one  recrystallization. 

The  mother  liquor  can  be  concentrated  by  evaporation  and 
more  crystals  obtained,  but  the  second  and  subsequent  crops  of 
dichromate  are  difficult  to  purify  because  they  are  so  largely  con- 
taminated with  potassium  sulphate. 

Beautiful  crystals  of  potassium  dichromate  can  be  easily  ob- 
tained by  recrystallizing  it  from  a  solution  of  i  part  of  the 
salt  in  10  parts  of  water,  allowing  the  filtered  solution  to  evapo- 
rate spontaneously. 

Turbidated  potassium  dichromate  may  be  conveniently  pre- 
pared from  a  solution  of  i  part  of  the  salt  in  5  parts  of  boiling 
water. 

The  mother  liquors  obtained  in  recrystallizing  and  in  turbidat- 
ing  the  dichromate  yield  all  of  the  salt  they  contain,  on  evaporation 
to  dryness. 

Description. — Large,  clear,  transparent,  orange-red  crystals; 
odorless ;  taste,  bitter,  metallic.  Soluble  in  TO  parts  of  water  at 
15°,  and  in  1.5  parts  of  boiling  water.  Insoluble  in  alcohol. 

The  water-solution  turns  blue  litmus  paper  red. 


544  POTASSIUM  CHROMATE. 

POTASSIUM  CHROMATE. 

POTASSII    CHROMAS. 

=  194.5. 

Potassium    dichromate 10  parts 

Potassium    carbonate 5  parts 

Water. 

Put  the  potassium  dichromate  in  a  porcelain  dish  with  30  parts 
of  water.  Heat  to  about  80°.  Add  the  potassium  carbonate,  in 
small  portions  at  a  time,  stirring  well.  When  all  of  the  carbonate 
has  been  added  heat  the  liquid  to  boiling",  add  20  parts  of  water, 
filter,  and  evaporate  to  crystallization.  Drain  and  dry  the  crys- 
tals with  the  aid  of  moderate  heat. 

Recover  the  remainder  of  the  salt  from  the  mother  liquor  in 
the  usual  way. 

Reaction.     K2Cr2O7+K2CO3=2K2CrO4+CO2. 

Description. — Yellow  translucent  crystals.  Soluble  in  about  1.5 
parts  of  water  at  15°. 

POTASSIUM  FERRICYANIDE. 

POTASSII    FERRICYANIDUM. 

K6Fe(CN)12— 658. 

Potassium   ferrocyanide 100  parts 

Lead  dioxide. 
Water. 

Dissolve  the  ferrocyanide  in  150  parts  of  water,  with  the  aid  of 
heat,  in  a  flask  capable  of  holding  about  600  parts  of  water. 
Pass  a  current  of  carbon  dioxide  into  the  solution  heated  to 
the  boiling  point.  Add  10  parts  of  lead  dioxide  to  the  hot 
solution,  and  stir  well.  Boil  for  an  hour  or  longer,  passing  a 
stream  of  carbon  dioxide  into  the  liquid  during  that  time. 

Should  the  precipitated  lead  carbonate  cause  too  violent  bump- 
ing remove  it  by  filtering  the  hot  liquid  through  a  muslin  filter, 


POTASSIUM    FERRIC  VAN  IDE.  545 

add  a  fresh  portion  of  10  parts  of  lead  dioxide,  boil  again,  and 
continue  passing  carbon  dioxide  into  the  liquid. 

Repeat  this  treatment  with  lead  dioxide  and  carbon  dioxide 
until  the  filtered  solution  no  longer  gives  a  blue  precipitate  with 
solution  of  ferric  chloride.  Then  let  the  solution  cool  in  a  cov- 
ered vessel.  Decant  the  clear  liquid  from  any  crystals  which 
may  have  separated.  Collect  the  crystals.  Evaporate  the  solu- 
tion over  a  water-bath  until  crystals  begin  to  be  formed  on  the 
surface.  Then  add  a  small  quantity  of  hot  water  to  redissolve 
the  crystals,  and  filter  the  liquid  while  hot  to  separate  the  pre- 
cipitate formed  during  the  evaporation.  Set  the  filtrate  aside 
in  a  covered  vessel  to  cool  and  crystallize  as  before.  Collect  the 
second  crop  of  crystals  and  add  it  to  the  first.  Drain  and  dry  the 
crystallized  product. 

Reaction.  4K4Fe  ( CN )  6H-2PbO2+4CO2+2H2O=4KHCO3+ 
2PbO+2K6Fe2(CN)12. 

Notes.  Several  crops  of  crystals  may  be  collected  from  the 
successive  mother-liquors  on  their  evaporation.  Should  yellow 
crystals  of  ferrocyanide  begin  to  be  formed,  repeat  the  boiling 
with  lead  dioxide  and  treatment  with  carbon  dioxide.  The  recov- 
ery of  ferricyanide  must  be  discontinued  as  soon  as  the  product 
becomes  contaminated  with  potassium  bicarbonate. 

Recrystallization  may  be  necessary  to  render  the  product,  or 
later  crops  of  it,  clean  and  pure. 

Description. — Clear,  transparent,  blood-red  crystals,  freely  solu- 
ble in  water,  forming  a  greenish-yellow  solution. 


POTASSIUM  FERROCYANIDE. 

POTASSII  FERROCYANIDUM. 

(Yellow  Prussiate  of  Potash.) 
K4Fe(CN)G.3H20^422. 

Large,  transparent,  pale  yellow,  soft,  odorless  crystals,  having 
a  saline  taste.  Slightly  efflorescent.  Soluble  in  4  parts  of  water 
at  15°,  and  in  2  parts  of  boiling  water.  Insoluble  in  alcohol. 

Vol.    11—35 


546  POTASSIUM   FEKROCYANIDE. 

Recrystallized  Potassium   F  err  o  cyanide. 

Yellow  prussiate  of  potash  ................  I  part 

Water    .................................  4  parts 

Dissolve  with  the  aid  of  heat.  Filter.  Crystallize  at  rest  by 
spontaneous  evaporation. 

Very  large  crystals  can  be  obtained.  Turn  the  crystals  now 
and  then  to  permit  their  development  in  all  directions. 

Description.  —  Large,  soft,  transparent,  light-yellow  crystals, 
odorless,  of  mild  saline  taste.  Soluble  in  4  parts  of  water  at  15°, 
and  in  2  parts  of  boiling  water.  Insoluble  in  alcohol.  The  water- 
solution  is  neutral  to  litmus  paper. 

POTASSIUM  HYDROXIDE. 

POTASSII    HYDROXIDUM. 

("Potassa.") 


A  strong  solution  of  potassium  hydroxide,  prepared  as  de- 
scribed below,  may  be  evaporated  to  dryness,  and  the  residue 
purified  with  alcohol. 

When  impure  potassium  hydroxide  is  dissolved  in  alcohol,  any 
carbonate,  sulphate,  and  the  greater  portion  of  any  chloride  pres- 
ent remain  undissolved,  and  may  thus  be  removed.  The  alcohol 
may  then  be  distilled  off  from  the  clear,  decanted  solution,  and 
the  remaining  mass  is  dried  and  fused  in  a  silver  capsule.  Al- 
though the  solution  is  brown  from  the  action  of  the  alkali  upon 
the  organic  substances  in  the  alcohol,  the  fused  potassium  hydrox- 
ide will  still  be  white.  To  prevent  the  formation  of  carbonate, 
a  little  boiled  distilled  water,  is  added  from  time  to  time  to  the 
alcoholic  solution  during  its  evaporation. 

Notes.  Potassium  hydroxide  must  be  kept  in  bottles  of  hard 
glass,  as  it  attacks  soft  glass.  Green  glass  free  from  lead  is  best. 
Glass  stoppers  in  bottles  containing  potassium  hydroxide  or  its 
solution,  are  acted  upon  by  the  alkali,  and  often  become  so  firmly 
fastened  to  the  neck  that  they  cannot  be  removed.  To  prevent  this 
a  little  petrolatum  may  be  rubbed  upon  the  stopper  before  inserting 


POTASSIUM    HYDROXIDE.  547 

it.     This  also  effectually  excludes  air,  and  thus  protects  the  potas- 
sium hydroxide  from  moisture  and  carbonic  acid. 

Description.— Dry,  white,  translucent,  hard,  brittle,  odorless, 
very  acrid,  caustic,  corrosive,  rapidly  deliquescent  when  exposed. 
Soluble  at  15°  in  half  its  weight  of  water,  and  in  twice  its  weight 
of  alcohol.  Freely  soluble  in  boiling  water  and  in  boiling  alcohol. 
Intensely  alkaline. 

Potassium  Hydroxide  Solution. 

LIQUOR  POTASSII   HYDROXIDI. 

Solution  of  Potassa. 

An  aqueous  solution  containing  about  5  per  cent,  of  potassium 
hydroxide  (KOH,  56.) 

Potassium     bicarbonate 90  Gm. 

Lime    40  Gm. 

Distilled  water,  sufficient. 

Dissolve  the  potassium  bicarbonate  in  400  ml  of  distilled  water, 
heat  the  solution  until  effervescence  ceases,  and  then  raise  it  to 
boiling.  Slake  the  lime  and  make  it  into  a  smooth  mixture  with 
400  ml  of  distilled  water,  and  heat  it  to  boiling.  Then  gradually 
add  the  first  liquid  to  the  second  and  continue  the  boiling  for  ten 
minutes.  Remove  the  heat,  cover  the  vessel  tightly,  and,  when 
the  contents  are  cold,  add  enough  distilled  water  to  make  the 
whole  weigh  1,000  Gm.  Lastly,  strain  through  linen,  or  remove 
the  clear  solution,  after  subsidence  of  the  precipitate,  by  means  of 
a  syphon. 

Solution  of  potassium  hydroxide  should  be  kept  in  well  stop- 
pered bottles. 

Reaction.  The  potassium  bicarbonate  is  first  converted  into 
normal  carbonate  by  boiling  the  solution.  Then,  K.,CO3+ 
Ca(OH)2=2KOH+CaCO,, 

Notes.  The  potassium  bicarbonate  is  used  in  preference  to 
monocarbonate,  because  bicarbonate  is  readily  obtained  nearly 
pure,  whereas  carbonate  usually  contains  various  impurities.  The 
lime  is  used  in  considerable  excess,  but  no  lime  will  be  contained 


548  POTASSIUM    HYDROXIDE. 

in  the  finished  solution  of  potassium  hydroxide,  as  calcium  hy- 
droxide is  insoluble  in  that  liquid.  Theoretically  I  part  of  lime  is 
sufficient  to  causticize  3.6  parts  of  potassium  bicarbonate  when 
the  process  is  conducted  as  prescribed  in  the  official  formula,  which 
is  the  one  given  above.  It  would  be  a  decided  improvement  upon 
this  process  to  first  wash  the  calcium  hydroxide,  throwing  away 
the  first  portion  of  water  used  as  in  the  process  for  making  lime 
water;  this  removes  dust,  salts,  etc.  An  unnecessarily  large  ex- 
cess of  lime  is  disadvantageous  in  that  the  calcium  hydroxide 
settles  more  slowly  than  the  carbonate. 

Potassium  carbonate  may  be  causticized  by  calcium  hydroxide 
without  the  aid  of  heat,  but  the  calcium  carbonate  then  formed 
is  very  light,  settles  slowly,  and  retains  much  liquid.  By  using  hot 
solutions,  as  directed  by  the  Pharmacopoeia,  a  much  more  dense 
calcium  carbonate  is  formed  which  settles  rapidly,  so  that  the 
solution  can  be  separated  with  less  waste. 

Not  less  than  8  parts,  and  preferably  12  parts  of  water  should 
be  taken  for  each  part  of  normal  potassium  carbonate  used.  The 
process  of  the  U.  S.  Pharmacopoeia  employs  about  io|  parts,  for 
90  parts  of  bicarbonate  corresponds  to  about  77  parts  of 
carbonate,  and  the  water  used  is  800  parts.  If  a  more  concen- 
trated solution  is  used  the  decomposition  will  be  incomplete.  The 
reaction  is  complete  when  the  liquid  no  longer  effervesces  with 
dilute  acid,  and  does  not  cause  a  turbidness  when  dropped  into 
clear  lime  water. 

Solution  of  potassium  hydroxide  can  well  be  evaporated  in  a 
clean,  bright  iron  pot  down  to  about  1.16  specific  weight  without 
danger  of  attacking  the  iron.  A  stronger  solution,  however, 
would  attack  the  metal.  In  any  event  a  solution  of  potassium 
hydroxide  should  not  be  allowed  to  remain  long  in  contact  with 
iron,  and  whenever  such  a  solution  is  to  be  concentrated  in  an 
iron  vessel,  the  evaporation  should  be  hastened  as  much  as 
possible. 

1  Straining  or  filtering  the  solution  is  liable  to  cause  its  discol- 
oration. It  is,  therefore,  best  to  let  it  stand  long  enough  to  be- 
come clear  by  subsidence  and  then  to  draw  off  the  clear  liquid 
by  means  of  a  glass  syphon. 

The  glass-stoppered  bottles  used  to  contain  it  should  be  made 
of  green  glass  free  from  lead,  and  the  stoppers  rubbed  with 
petrolatum. 


POTASSIUM    HYDROXIDE.  549 

Instead  of  directing  that  1,000  Gm.  of  the  solution  should  be 
made  out  of  90  Gm.  of  potassium  bicarbonate,  thus  making  the 
strength  of  the  product  depend  upon  the  amount  of  material  taken 
and  upon  the  care  exercised  in  the  management  of  the  details 
of  the  process,  the  Pharmacopoeia  ought  to  direct  that  the  strength 
be  determined  by  actual  test  with  volumetric  solution  of  sulphuric 
acid  before  it  is  finished  instead  of  afterwards,  and  the  prepara- 
tion adjusted,  by  dilution  with  distilled  water,  to  the  prescribed 
standard ;  in  other  words,  the  quantitative  test  should  be  a  part 
of  the  process  of  preparation. 

Description. — Clear,  colorless,  odorless,  acrid,  caustic,  strongly 
alkaline.  Sp.  w.  about  1.036  at  15°. 

Valuation.  To  neutralize  28  Gm.  of  the  official  solution  of 
potassium  hydroxide  (5%)  requires  25  ml  of  normal  sulphuric 
acid.  Each  ml  of  the  volumetric  sulphuric  acid  solution  indicates 
0.2  per  cent,  of  KOH.  Phenolphtalein  is  the  indicator  used.  One 
ml  of  normal  sulphuric  acid  is  the  equivalent  of  0.05599  Gm. 
of  KOH. 

Potassa  with  Lime. 

POTASSA   CUM    CALCE. 

Potassa ' i  part 

Lime    I  part 

Rub  them  together,  in  a  warm  iron  mortar,  so  as  to  form  a 
powder,  and  keep  it  in  a  well-stoppered  bottle. 

Notes.  The  lime  prevents  the  potassium  hydroxide  from  ab- 
sorbing carbon  dioxide  from  the  air  to  form  carbonate.  The 
mixture  is,  however,  less  caustic  and  corrosive  than  potassium 
hydroxide  alone.  The  glass  stopper  of  the  bottle  in  which  the 
preparation  is  kept  should  be  coated  with  petrolatum. 

Description. — A  grayish-white  powder,  deliquescent,  having  a 
strongly  alkaline  reaction,  and  responding  to  the  tests  for  calcium 
and  potassium.  It  should  be  soluble  in  diluted  hydrochloric  acid 
without  leaving  more  than  a  small  residue. 


550  POTASSIUM   HYPOPHOSPHITE. 

POTASSIUM   HYPOPHOSPHITE. 

POTASSII  HYPOPHOSPHIS. 

KPO2H2=io4. 

Calcium    hypophosphite I  part 

Potassium    carbonate I  part 

Dissolve  each  salt  separately  in  /  parts  of  boiling  water.  Mix 
the  solutions.  Filter  off  the  calcium  carbonate,  and  evaporate  the 
filtrate  to  dryness,  over  a  water-bath,  stirring  constantly  so  as 
to  obtain  a  granular  product. 

Notes.  The  temperature  during  the  evaporation  should  not 
exceed  85°  C,  as  hypophosphites  are  prone  to  decompose  with 
violent  explosion  when  heated  to  nearly  100°  C.,  or  higher. 

The  product  may  be  freed  from  potassium  carbonate  and  other 
impurities  by  dissolving  it  in  ten  times  its  weight  of  alcohol,  filter- 
ing, evaporating  the  solution  to  the  consistence  of  thick  syrup, 
and  setting  this  aside  to  solidify  into  a  crystalline  mass. 

Reaction.     Ca  ( PO2H2)  2+K2CO3=CaCO3+2KPO2H2. 

Description. — A  white  granular  salt,  easily  soluble  in  water  and 
weak  alcohol.  It  may  be  obtained  in  crystalline  form  from  the 
aqueous  solution. 

POTASSIUM  HYPOTHIOSULPHITE. 

POTASSA   SULPHURATA. 

Sulphurated  Potassa. 
(Liver  of  Sulphur.) 

Sublimed  sulphur   I  part 

Potassium    carbonate 2.  parts 

Mix  by  trituration.  Heat  the  mixture  gradually  in  a  covered 
crucible,  which  should  be  only  half-filled,  until  the  mass  ceases 
to  swell  and  is  completely  melted.  Then  pour  the  molten  mass 
upon  a  cold  stone  or  glass  slab,  and,  when  it  has  become  hard 


SULPHURATED  POTASSA.  551 

and  nearly  cold,  break  it  into  pieces  and  keep  it  in  a  dry  bottle 
of  hard  glass  which  must  be  tightly  closed. 

Reaction.  When  the  proportions  of  the  materials  are  as  here 
given,  the  reaction  is  frequently  represented  as  4K2CO,4-ioS= 
3K2SS2+K2SO4-f  4CO2 ;  but  the  following  is  probably  the  prin- 
cipal reaction :  3K2c63+8S2=K2S2O3+2K2SS2+3CO2.  The 
composition  of  the  product  depends  much  upon  the  temperature, 
which  should  not  be  too  high.  It  is  quite  probable  that  sulphur 
is  soluble  in  fused  potassium  sulphide  (K2S)  as  well  as  in  a 
water  solution  of  it.  The  proportion  of  sulphur  used  is  in  some 
formulas  greater  and  in  others  less ;  yet  the  product  is  in  each 
case  physically  homogeneous.  When  a  solution  of  sulphurated 
potassa,  U.  S.  P.,  is  mixed  with  a  solution  of  copper  sulphate 
the  reaction  between  them  is:  CuSO4+K2S3=CuS+K.,SO4-|-S.,. 
From  the  fact  that  only  one-third  of  the  sulphur  contained  in 
the  sulphurated  potassa  forms  CuS  in  this  case,  it  is  obvious  that 
the  sulphur  is  not  all  of  one  kind.  In  other  words  the  sulphur  in 
sulphurated  potassa  made  by  fusing  sulphur  and  potassium  car- 
bonate together  is  partly  positive  and  partly  negative,  as  would 
be  the  case  in  K2SS... 

Notes.  The  potassium  carbonate  and  the  sulphur  must  both  be 
quite  dry.  They  should  be  finely  powdered  and  well  mixed  in 
order  to  obtain  a  uniform  product.  It  is  well  to  pass  the  pow- 
dered mixture  through  a  sieve  of  about  600  meshes  to  the  square 
centimeter. 

A  covered  iron  dish  will  answer  well  for  the  fusion,  and  a 
moderate  heat  (from  150°  to  250°  C.)  should  be  used.  The  mass 
should  be  occasionally  stirred. 

The  heat  should  not  be  higher  than  is  necessary  to  fusion  with- 
out turning  the  mixture  into  a  thin  liquid. 

When  the  evolution  of  carbon  dioxide  ceases,  and  the  whole 
mass  fuses  quietly  and  completely,  a  sample  should  be  taken  out 
and  put  into  about  twice  its  weight  of  water;  when  it  dissolves 
entirely,  without  separation  of  sulphur,  the  fused  mass  is  allowed 
to  cool  somewhat,  and  is  then  poured  upon  a  slab  (or  into  an 
oiled  iron  dish),  and  covered  well  (with  a  bell  glass  or  an  inverted 
dish)  to  exclude  air  and  moisture,  until  nearly  cold.  It  is  then 
broken  and  immediately  transferred  to  a  dry  container. 

Description. — Liver  brown  pieces  having  a  bitter  alkaline  taste 


552  POTASSIUM  IODATE. 

and  an  odor  of  hydrogen  sulphide.  Hygroscopic  ;  soluble  in  twice 
its  weight  of  water  at  15°  C,  leaving  a  small  residue.  Alcohol 
dissolves  the  potassium  sulphide,  leaving  the  sulphate  and  thio- 
sulphate. 

POTASSIUM  IODATE. 

POTASSII    IODAS. 


Potassium     permanganate  ...............   2  parts 

Potassium    iodide  ......................    i  part 

Water, 
Alcohol, 
Acetic  Acid. 

Dissolve  the  permanganate  in  50  parts  of  hot  water,  add  the 
iodide  dissolved  in  2  parts  of  water,  heat  the  mixture  over  a 
water-bath  for  about  twenty  minutes  or  half  an  hour,  adding 
alcohol  drop  by  drop  at  the  end  until  the  liquid  is  decolorized, 
and  then  filter.  Wash  the  precipitated  potassium  maganite  on  the 
filter  and  add  the  washings  to  the  filtrate.  To  the  filtrate  add 
enough  acetic  acid  to  render  the  reaction  on  test-paper  distinctly 
acid.  Evaporate  the  liquid  to  about  1.5  parts  ;  let  it  cool  ;  separate 
the  crystals  from  the  mother-liquor,  wash  the  product  with  alcohol 
and  dry  it. 

Beaction.    KI+2KMnO4=KIO3+K2Mn2O5. 

Notes.  The  acidification  with  acetic  acid  is  necessary  to  prevent 
the  product  from  having  an  alkaline  reaction  due  to  adhering 
alkali,  which  it  is  extremely  difficult  to  wash  away. 

Description.  —  A  white,  granular,  crystalline  salt  of  perfectly 
neutral  reaction  to  test-paper. 

POTASSIUM  IODIDE. 

POTASSI  IODIDUM. 
0=165.5. 

Solution  of  potassium  hydroxide  ........  1,000     ml 

Iodine  ....................  100  Gm.,  or  sufficient 

Wood  charcoal,  in  fine  powder  ..........       15  Gm 

Boiling  distilled  water,  sufficient. 


POTASSIUM  IODIDE.  553 

Put  the  solution  of  potassium  hydroxide  in  a  flask,  add  the 
iodine,  a  little  at  a  time,  with  constant  agitation,  until  the  solution 
becomes  permanently  brown.  Evaporate  to  dryness.  Powder  the 
residue,  and  mix  it  well  with  the  charcoal.  Throw  the  mixture 
into  a  red-hot  iron  crucible,  and  when  the  whole  is  in  a  fused 
condition  pour  it  out  to  cool,  dissolve  it  in  200  ml  of  boiling  dis- 
tilled water,  filter,  and  evaporate  until  a  pellicle  forms.  Then  set 
aside  to  cool  and  crystallize.  Drain  the  crystals  and  dry  them  in 
a  warm  place.  The  remainder  of  the  salt  may  be  obtained  from 
the  mother  liquor  by  evaporation  to  dryness,  stirring  constantly. 

Reaction.     3l2+6KOH=5KI+KIO3+3H2O  ;  and  then, 
2KI03+3C==2KI+3C02. 

Notes.  The  red  brown  liquid  formed  by  dissolving  iodine  in 
solution  of  potassium  hydroxide  contains  potassium  iodide  and 
potassium  iodate,  as  seen  from  the  above  equation.  By  heating 
the  salt  mass  obtained  on  evaporation  of  this  liquid  to  dryness,  the 
iodate  is  reduced  to  iodide ;  but  the  heat  necessary  for  this  pur- 
pose is  so  high  that  loss  of  iodine  ensues,  and  the  product  be- 
comes alkaline.  To  prevent  this,  charcoal  is  added,  which  makes 
the  reduction  practicable  at  a  much  lower  temperature. 

The  crystallization  of  potassium  iodide  is  somewhat  dif- 
ficult. It  is  best  to  continue  the  evaporation  until  a  sam- 
ple of  the  liquid,  when  removed  from  the  vessel,  crystal- 
lizes on  cooling.  The  liquid  should  then  be  left  in  a  warm 
place  (50°  to  60°).,  where  the  evaporation  may  continue  spontane- 
ously in  order  that  large  crystals  may  be  obtained.  At  a  lower 
temperature  the  iodide  ascends  the  sides  of  the  vessel  and  creeps 
over  the  edges. 

When  perfectly  pure,  potassium  iodide  is  difficult  to  obtain  in 
colorless  crystals ;  it  undergoes  partial  decomposition  with  libera- 
tion of  enough  iodine  to  discolor  the  product.  To  prevent  this 
discoloration  the  liquid  is  usually  rendered  slightly  alkaline  be- 
fore being  set  aside  for  crystallization.  The  presence  of  potas- 
sium carbonate  not  only  facilitates  the  formation  of  crystals,  but 
also  renders  the  product  whiter.  The  pharmacopoeial  tests  per- 
mit a  slight  alkalinity  (less  than  o.i  per  cent).  Crystals  of  per- 
fectly pure  potassium  iodide  are  usually  not  quite  white,  but 
may  be  made  so  by  drying  at  120°  to  125°  C. 


554  POTASSIUM  IODIDE. 

Second  Method. 

Iron  wire,  cut 6  parts 

Iodine    20  parts 

Potassium  bicarbonate 16  parts 

Distilled  water,  sufficient. 

Digest  the  iron  and  15  parts  of  the  iodine  with  50  parts  of 
water  in  a  flask  until  all  odor  of  iodine  ceases  and  a  green  solution 
of  ferrous  iodide  results.  Filter  this,  and  in  the  filtrate  dissolve 
the  remainder  of  the  iodine. 

Put  the  potassium  bicarbonate  into  a  dish  with  80  parts  of  dis- 
tilled water,  heat  until  effervescence  ceases,  and  then  raise  the 
heat  to  boiling.  Add  slowly  to  this  boiling  hot  solution  the  filt- 
ered solution  of  the  iodides  or  iron.  Boil  the  mixture  for  fifteen 
minutes.  (If  all  the  iron  has  not  been  precipitated  from  the  so- 
lution, add  a  little  more  potassium  bicarbonate.)  Filter,  evapor- 
ate, and  crystallize. 

Reaction.     Fe+I2=FeI2;   then  3FeI2+I2=FeI2.2FeI3 ;  finally 
FeI2.2FeI3+4K2CO8=8KI+FeO.Fe2O3+4CO2. 

Notes.  As  seen  from  the  equation,  a  solution  of  ferrous  iodide 
is  first  made.  This  can  be  at  once  treated  with  potassium  car- 
bonate to  obtain  the  potassium  iodide: 

FeI2+K2CO3==2KI+FeCO3. 

But  in  this  case  the  iron  is  separated  with  greater  difficulty, 
being  first  thrown  down  as  ferrous  carbonate,  which  at  once 
begins  to  lose  carbonic  acid,  and  at  the  same  time  oxidizes  so 
that  the  precipitate  gradually  changes  from  light  gray  to  blue, 
yellowish  brown,  and  finally  to  brown  ferric  hydroxide  Fe(OH)3. 
All  of  the  iron  does  not  separate  at  once,  however,  so  that  during 
the  subsequent  evaporation  of  the  filtered  solution  of  iodide  of 
potassium  a  considerable  quantity  of  flocculent  deposit  of  ferric 
hydroxide  makes  its  appearance  and  must  be  filtered  out. 

This  difficulty  may  be  remedied  to  a  great  extent  by  convert- 
ing the  ferrous  iodide  into  ferrico-ferrous  iodide  by  adding  the 
required  additional  quantity  of  iodine.  The  precipitate  will  then, 
after  the  boiling,  be  black  magnetic  oxide  of  iron,  which  is  very 
dense  and,  therefore,  more  easily  separated  than  ferric  hydroxide. 


POTASSIUM  IODIDE.  555 

When  the  solution  of  iodide  of  iron  has  all  been  added  to  the 
hot  solution  of  potassium  carbonate,  the  liquid  should  have  a 
neutral  or  faintly  alkaline  reaction.  Should  it  instead  be  acid, 
add  more  potassium  bicarbonate.  If  too  alkaline  add  some  hy- 
driodic  acid  prepared  from  tartaric  acid  and  KI. 

Third  Method. 

Red  phosphorus i  part 

Iodine 12  parts 

Potassium   carbonate 6  parts 

Distilled  water,  sufficient. 

Put  the  phosphorus  in  a  porcelain  dish  with  35  parts  of  dis- 
tilled water  and  warm  the  liquid  over  a  water-bath  to  about 
40°  C.  Add  the  iodine  a  little  at  a  time,  stirring  gently,  until 
the  liquid  becomes  permanently  colored. 

Decant  the  clear  solution  from  the  residue,  wash  the  latter  with 
a  little  distilled  water,  and  add  the  washings  to  the  decanted 
solution. 

Add  enough  calcium  hydroxide  mixed  with  water  ("milk  of 
lime")  to  impart  a  slightly  alkaline  reaction  to  the  liquid. 

Filter  the  solution,  and  add  the  potassium  carbonate  dissolved 
in  10  parts  of  water,  stirring  well. 

Decant  the  liquid  from  the  precipitate,  wash  the  latter  with 
some  distilled  water,  add  the  washings  to  the  decanted  solution, 
and  filter  the  liquid. 

Evaporate  the  solution  to  crystallization. 

Reactions.  The  first  reactions  result  in  the  formation  of  PL 
and  PI5.  Then :  PI3+3H2O=H3PO3-f 3HI ;  and 

H8PO8+I2+H2O=H3PO4+2HI.     At   the   same   time   this   re- 
action  occurs:     PI5+4H2O=H3PO4+5HI.     Hence  two   mole- 
cules of  H3PO4  and  ten  molecules  of  HI  are  the  final  products. 
When  calcium  hydroxide  is  added  the  reactions  are: 

2HI+Ca(OH)2=CaI2+2H2O  and 
H8P04+Ca(OH)3=CaHP04+2H20  and 
2CaHP04+Ca  ( OH )  2=Ca3  ( PO4)  2+2H2O. 


556  POTASSIUM  IODIDE. 

When  the  calcium  phosphate  has  been  filtered  out  and  the  po- 
tassium carbonate  is  added  to  the  solution  of  CaI2  the  reaction  is : 

CaI2+K2CO8= 2KI-fCaCO3. 

Notes.  The  use  of  red  instead  of  ordinary  phosphorus  lessens 
the  danger  involved  in  this  process. .  But  great  care  should  be  ex- 
ercised lest  the  phosphorus  iodides  decompose  with  violence. 
After  the  addition  of  the  prescribed  amount  of  potassium  car- 
bonate to  the  solution  of  calcium  iodide,  the  filtered  liquid  should 
be  tested  with  a  few  drops  of  potassium  carbonate  solution,  and, 
if  further  precipitation  is  caused  thereby,  more  potassium  car- 
bonate solution  should  be  cautiously  added,  a  little  at  a  time, 
stirring  well,  until  precipitation  is  no  longer  produced  by  it. 

The  final  solution,  before  evaporation,  should  be  of  a  slightly 
alkaline  reaction.  Instead  of  evaporating  to  crystallization  the 
salt  may  be  granulated. 

Description. — Colorless  or  white  translucent  cubical  crystals  or 
a  granular  crystalline  powder,  with  a  faint  iodine-like  odor  and 
pungent,  saline,  bitterish  taste.  Slightly  hygroscopic.  Soluble 
at  15°  in  0.75  part  of  water  and  in  18  parts  of  alcohol;  in  0.5 
part  of  boiling  water,  and  in  6  parts  of  boiling  alcohol.  The 
water-solution  has  a  neutral  or  only  faintly  alkaline  reaction  on 
test-paper. 

POTASSIUM    NITRATE. 

POTASSII    NITRAS. 
KNO8=IOI. 

Potassium  chloride 6  parts 

Sodium   nitrate 7  parts 

Water. 

Mix  the  salts  in  a  porcelain  dish  with  12  parts  of  water.  Heat 
at  the  boiling  point,  stirring  well  and  without  interruption  for 
several  minutes.  Filter.  Evaporate  the  filtrate  to  8  parts.  Should 
any  salt  separate  during  the  evaporation  heat  the  liquid  to  boil- 
ing and  filter  again.  Let  the  filtrate  stand  several  hours.  Col- 
lect the  crystals  of  potassium  nitrate  and  recrystallize  several 
times  to  remove  adhering  sodium  chloride.  Dry  the  product  per- 
fectly. 


POTASSIUM  NITRATE.  557 

Reaction.     KCl+NaNO3=KNO3+NaCl. 

Notes.  No  reaction  takes  place  until  the  solution  is  boiled 
down.  But  the  process  is  based  upon  the  differences  in  the  re- 
spective solubilities  of  sodium  chloride  and  potassium  nitrate  at 
different  temperatures.  Potassium  nitrate  is  less  readily  soluble 
in  cold  water  than  the  chlorides  of  potassium  and  sodium,  but 
far  more  freely  soluble  than  the  chlorides  in  hot  water.  Thus  the 
sodium  chloride  crystallizes  out  from  the  hot  saturated  solution 
of  potassium  nitrate.  The  separation  of  the  sodium  chloride  is 
facilitated  by  having  the  sodium  nitrate  in  excess ;  but  the  prod- 
uct should  be  washed  with  a  cold  saturated  solution  of  potassium 
nitrate  to  remove  the  last  traces  of  chlorides  and  sodium  nitrate. 

Commercial  potassium  nitrate  may  be  purified  by  dissolving- 
it  in  an  equal  weight  of  boiling  distilled  water,  filtering,  and  stir- 
ring the  filtrate  constantly  until  cool.  The  saltpeter  should  first 
be  coarsely  powdered  to  facilitate  its  solution. 

When  cool,  set  it  aside  for  some  hours.  Collect  the  crystals 
on  a  filter,  and  let  drain.  Wash  twice  by  rapidly  passing  small 
quantities  of  distilled  water  over  the  crystals,  allowing  all  of  the 
wash-water  to  pass  through  before  adding  more.  When  the 
washings  no  longer  give  a  decided  reaction  for  chlorides  (with 
test  solution  of  silver  nitrate),  collect  the  crystals  and  dry  them 
between  blotting  paper,  or  on  suitable  trays  covered  with  muslin. 

Evaporate  the  mother  liquor  at  about  95°  C.  to  one-third  its 
bulk,  and  let  cool  during  constant  stirring.  Wash  the  second 
crop  of  crystals  as  before,  drain,  and  dry  as  before,  and  add  them 
to  the  first  crop.  Repeat  this  operation  as  often  as  may  be 
profitable. 

To  simply  granulate  potassium  nitrate  it  may  be  dissolved  in  an 
equal  weight  of  boiling  distilled  water,  the  solution  filtered,  and 
the  filtrate  evaporated,  stirring  constantly  with  a  glass  rod  or 
porcelain  spatula  until  a  dry,  granular  salt  remains. 

Description. — Colorless  crystals,  or  a  crystalline  granular  pow- 
der, odorless,  and  of  a  cooling,  saline,  pungent  taste.  Soluble  in 
3.8  parts  of  water  at  15°,  and  in  0.4  part  of  boiling  water.  Very 
sparingly  soluble  in  alcohol.  Alcohol  of  80%  strength  dissolves 
less  than  one-half  of  one  per  cent  of  its  own  weight  of  potassium 
nitrate ;  100  parts  of  alcohol  of  50%  strength  dissolves  only  2.8 


558  POTASSIUM  NITRATE. 

parts  of  the  salt,  and  100  parts  of  alcohol  of  10%  strength  13.2 
parts.  • 

Turbidated  Potassium  Nitrate. 

Potassium  nitrate I  part 

Boiling   water 2  parts 

Dissolve,  filter,  and  stir  until  cold.  Collect,  drain,  and  dry  the 
crystals. 

Evaporate  the  mother-liquor  nearly  to  dryness,  stirring  con- 
stantly, and  dry  the  residue,  which  should  be  collected  separately, 
or  turbidated  as  before  if  the  quantity  is  sufficient  to  render  it 
advantageous. 

POTASSIUM    OLEATE. 

Soft  Soap. 
[Sapo  Mollis.     Green  Soap.     Potash  Soap.] 

Linseed   oil 400  Gm 

Potassium  hydroxide   (90%) 90  Gm 

Alcohol 40  ml 

Water,  sufficient. 

Heat  the  oil  in  a  deep  porcelain  dish  on  a  water-bath  to  a  tem- 
perature of  about  60°  C.  Dissolve  the  potassium  hydroxide  in 
450  ml  of  water,  add  the  alcohol  to  the  solution,  and  then  gradu- 
ally add  this  mixture  to  the  oil,  stirring  constantly,  continuing 
the  heat  and  stirring  until  the  product  becomes  perfectly  soluble 
in  boiling  water  without  the  separation  of  oily  drops  (which  may 
be  ascertained  by  tasting  a  small  portion  from  time  to  time). 
Then  allow  the  product  to  cool  and  transfer  it  to  suitable  con- 
tainers. 

Description. — A  soft,  brownish-yellow  solid,  translucent  in  thin 
layers.  Should  make  an  almost  clear  solution  in  5  parts  of  water. 
Should  dissolve  in  2  parts  of  hot  alcohol,  leaving  not  over  3  per 
cent  of  undissolved  residue. 


POTASSIUM   OXALATE.  559 

POTASSIUM    OXALATE;    NORMAL. 

POTASSII    OXALAS. 
K2C204.2H20=202. 

Oxalic  acid 63  parts 

Potassium  bicarbonate 100  parts 

Distilled    water 500  parts 

Dissolve  the  oxalic  acid  in  the  water  by  the  aid  of  heat;  then 
add  the  potassium  bicarbonate.  Neutralize  perfectly.  Evaporate 
and  crystallize. 

Keaction.     2KHCO3+H2C2O4=K2C2O4+2H2O+2OX 

Description. — Transparent  prisms  or  pyramids,  easily  soluble  in 
water. 

ACID    POTASSIUM    OXALATE. 
KHC204.2H20=i62. 

Oxalic   acid 126  Gm 

Potassium  bicarbonate 100  Gm 

Distilled  water 1,000  ml 

Dissolve  the  potassium  bicarbonate  in  the  water  by  the  aid  of 
heat,  boiling  the  liquid  until  effervescence  ceases ;  then  add  the 
oxalic  acid,  dissolve,  filter  while  hot,  and  set  aside  to  cool  and 
crystallize. 

Reactions.     2KHCO3=K,CO3+H2O-fCO2 ;  then, 
K2C03+2H2C204=2KHC204+H20+C02. 

Description. — Occurs  usually  as  anhydrous  prisms  or  crystal- 
lized with  one  or  two  molecules  of  water. 
It  is  not  readily  soluble  in  cold  water. 


560  POTASSIUM  PERMANGANATE. 

POTASSIUM    PERMANGANATE. 

POTASSII    PERMANGANAS. 


Manganese    dioxide  ....................  60  parts 

Potassium   hydroxide  .....  .  ............  70  parts 

Potassium   chlorate  ....................  35  parts 

Water. 

Heat  the  finely  powdered  manganese  dioxide  to  a  red  heat. 
Let  it  cool  again.  Put  the  potassium  hydroxide  in  a  porcelain 
dish,  add  100  parts  of  water,  and  then  the  potassium  chlorate. 
Heat  until  solution  is  effected.  Then  add  the  manganese  dioxide. 
Evaporate  the  mixture  to  a  thick  pasty  mass,  stirring  constantly 
during  the  evaporation  to  make  the  mixture  uniform.  Heat  the 
paste  to  redness  in  an  iron  crucible  or  dish,  which  should  not  be 
more  than  half  filled  as  the  mass  swells  on  heating.  When  water 
vapors  cease  to  escape  and  the  mass  becomes  dark  green  or  brown 
and  quite  hard,  let  it.  cool,  remove  it  from  the  crucible  or  dish, 
and  powder  it.  Mix  it  with  about  350  parts  of  water,  boil  the 
mixture  for  an  hour,  passing  a  current  of  carbon  dioxide  into 
the  boiling  liquid  during  that  period.  The  green  color  of  the 
liquid  is  changed  to  violet  by  this  treatment  and  a  brown  precipi- 
tate is  thrown  down.  Set  the  liquid  aside  until  the  precipitate  has 
subsided.  Filter  the  solution  through  asbestos  or  glass  wool. 
Wash  the  precipitate  with  a  small  quantity  of  hot  water,  and  add 
the  washings  to  the  other  filtrate.  Evaporate  rapidly  until  crys- 
tals begin  to  separate.  Then  allow  the  solution  to  cool  in  a  well 
covered  vessel.  Collect  the  crystals.  Evaporate  the  mother- 
liquor,  after  adding  a  little  hydrochloric  or  sulphuric  acid  to  it, 
and  again  let  crystals  be  formed.  Recrystallize  this  second  crop 
of  crystals  before  adding  it  to  the  first.  Drain  the  crystals  by 
suction  and  dry  them  over  sulphuric  acid. 

Reactions. 

3MnO2+6KOH4-KClO3=3K2MnO4+KCl+3H2O  ;  then, 
3K2MnO4+2H2O=2KMnO4+MnOg+4KQH  ;  and, 
KOH+CO2=KHCO3. 


POTASSIUM   PHOSPHATE.  561 

Description.  —  Slender,  opaque,  dark  purple,  lustrous  crystals, 
odorless;  taste  sweetish,  disagreeable,  astringent.  Soluble  in  16 
parts  of  water  at  15°,  and  in  3  parts  of  boiling  water.  Decom- 
posed in  contact  with  alcohol.  Explosive  with  glycerine. 

POTASSIUM    PHOSPHATE. 

POTASSII    PHOSPHAS. 


Prepared  in  the  same  manner  as  sodium  phosphate,  using 
potassium  carbonate  to  decompose  the  acid  phosphate  of  calcium. 

Potassium  phosphate  is  a  deliquescent,  indistinctly  crystalline, 
white  mass,  very  freely  soluble  in  water.  At  red  heat  it  is  con- 
verted into  pyrophosphate  of  potassium,  which  is  also  deliques- 
cent. 

POTASSIUM    SALICYLATE. 

POTASSII    SALICYLAS. 


Potassium   bicarbonate  ................     29  parts 

Salicylic   acid  ........................     41  parts 

Distilled   water  .......................    150  parts 

Dissolve,  filter,  evaporate  to  dryness. 
White,  odorless,  acrid  ;  freely  soluble 

POTASSIUM-SODIUM    TARTRATE, 

POTASSII    ET    SODII    TARTRAS. 

Rochelle  Salt. 

[The    British    Pharmacopoeia    calls    Rochelle    Salt    "Tartarated 

Soda."] 

KNaC4H406.4H20=282. 

Potassium  bitartrate  ...................     5  parts 

Sodium  carbonate  .....'  ................     4  parts 

Distilled   water  ........................   20  parts 

Heat  the  water  to  boiling  in  a  porcelain  dish  ;  add  the  sodium 
carbonate,  and  when  that  is  dissolved,  gradually  add  the  cream 

Vol.  11-36 


562  ROCHELLE   SALT. 

of  tartar,  and  continue  heating  until  all  is  dissolved.  Set  the 
solution  aside  for  a  day  or  two.  Then  filter,  evaporate  the  filtrate 
to  nine  parts,  or  until  a  pellicle  forms,  and  then  set  it  aside  to  crys- 
tallize. 

Reaction. 
2KHC4H4O6+Na2CO3=2KNaC4H4O6+H2O+CO2. 

Notes.  A  slight  excess  of  sodium  carbonate  is  prescribed,  be- 
cause the  salt  crystallizes  best  from  a  slightly  alkaline  solution. 
Any  excess  of  sodium  carbonate  will  remain  in  the  mother  liquor. 
Large  crystals  are  easily  obtained.  The  crystals  should  be  hastily 
rinsed  with  a  little  cold  distilled  water.  The  mother  liquor  is 
usually  colored,  more  so  the  farther  the  evaporation  is  carried. 
(See,  also,  Potassium  Tartrate.) 

The  direction  to  allow  the  solution  to  stand  some  time  before 
filtering  and  evaporating  to  crystallization,  has  for  its  object  the 
deposition  of  any  calcium  tartrate  and  carbonate. 

The  crystals  must  be  dried  without  the  aid  of  heat. 

After  several  crystallizations,  the  mother-liquor  becomes  col- 
ored. It  may  be  decolorized  with  animal  charcoal  if  the  quan- 
tity operated  upon  justifies  it.  The  tartaric  acid  in  the  last 
mother-liquor  may  be  recovered  in  the  form  of  cream  of  tartar 
by  precipitation  with  hydrochloric  acid. 

Description.  —  Colorless,  transparent  prisms,  or  a  white  powder  ; 
odorless  ;  taste  cooling,  saline.  Slightly  efflorescent  in  warm,  dry 
air.  Soluble  in  1.4  parts  of  water  at  15°,  and  in  less  than  its  own 
weight  of  boiling  water.  Practically  insoluble  in  alcohol.  Neu- 
tral to  litmus  paper. 

POTASSIUM    THIOCYANATE. 

POTASSII    THIOCYANAS. 

(Potassium  Sulphocyanate.     Rhodankalium.) 


Anhydrous  potassium  f  errocyanide  ......  46  parts 

Potassium  carbonate  ...................  17  parts 

Washed    sulphur  ......................  32  parts 

Alcohol. 


POTASSIUM  THIOCYANATE.  563 

Mix  the  thoroughly  dried  and  powdered  solids  very  intimately 
by  triturating  them  together  in  a  mortar.  Heat  the  mixture 
slowly  until  the  mass  fuses.  Let  it  cool.  Extract  the  thiocyanate 
with  hot  alcohol  and  collect  the  crystals  which  deposit  on  cooling. 
Evaporate  the  mother-liquor  to  obtain  more. 

Notes.  For  directions  how  to  make  the  anhydrous  potassium 
ferrocyanide  see  notes  under  potassium  cyanate. 

Description. — A  white  crystalline  salt,  of  bitter  saline  taste. 
Readily  water-soluble. 


POTASSIUM    SULPHATE. 

POTASSII    SULPHAS. 


Diluted  sulphuric  acid  ................    100  parts 

Potassium  bicarbonate  .......  .  .........     20  parts 

Place  the  acid  in  a  porcelain  dish  and  neutralize  it  with  the 
potassium  bicarbonate,  gradually  added,  stirring  after  each  ad- 
dition until  effervescence  has  ceased  before  adding  more.  Try 
the  solution  with  test-paper,  and  add  more  potassium  bicarbonate 
if  necessary  to  render  the  reaction  quite  neutral.  Filter  the  solu- 
tion and  evaporate  to  crystallization. 

Reaction.     2KHCOS+H2SO4=K2SO4+2H2O+2CO2. 

Description.  —  Colorless,  odorless  crystals  of  a  somewhat  bitter- 
ish saline  taste.  Soluble  in  9.5  parts  of  water  at  15°,  and  in  4 
parts  of  boiling  water.  Insoluble  in  alcohol. 

POTASSIUM    SULPHITE. 

POTASSII    SULPHIS. 

K2SO.,.2H2O=i94. 

Prepared  by  passing  sulphurous  oxide  into  a  solution  of  po- 
tassium carbonate  until  all  carbonic  acid  has  been  expelled,  and 
then  adding  another  equal  quantity  of  potassium  carbonate.  The 


564  POTASSIUM   SULPHITE. 

solution  is  then  evaporated  to  crystallization.     See  Sodium  Sul- 
phite. 

Description. — Colorless  crystals  or  powder,  readily  soluble  in 
water,  and  but  slightly  in  alcohol.  Decomposed  by  acids  yielding 
SO2  without  deposit  of  sulphur. 


POTASSIUM    TARTRATE. 

POTASSII   TARTRAS. 

K2C4H4O6.H2O=47o. 

Potassium  bicarbonate 15  parts 

Cream  of  tartar 28  parts 

Distilled  water. 

Dissolve  the  potassium  bicarbonate  in  50  parts  of  water  with 
the  aid  of  sufficient  heat  to  cause  effervescence.  Raise  the  tem- 
perature of  the  liquid  to  the  boiling  point.  Add  the  cream  of 
tartar  in  small  portions  at  a  time,  stirring  well  until  all  has  dis- 
solved, leaving  the  liquid  faintly  alkaline  in  its  reaction  on  test- 
paper.  Filter.  Evaporate  the  nitrate  until  signs  of  crystalliza- 
tion appear.  Then  set  the  dish  aside  for  three  or  four  days  in 
a  cold  place.  Collect  the  crystals  in  a  funnel  and  let  them  be 
well  drained. 

Evaporate  the  mother  liquor  over  a  water-bath  to  one-third  of 
its  volume  and  again  set  aside  to  crystallize. 

Dry  the  crystals  by  moderate  heat. 

Keep  the  product  in  a  tightly  closed  bottle. 

Reaction. 

K2CO3+2KHC4H4O6=2K2C4H4O6.H2O+CO2. 

Notes.  Should  the  reaction  of  the  solution  not  be  faintly  alka- 
line, make  it  so  by  the  addition  of  more  of  the  carbonate  or  the 
tartrate  as  may  be  required.  The  salt  crystallizes  best  from  a 
slightly  alkaline  solution. 

When  colorless  crystals  can  no  longer  be  obtained  from  the 
mother-liquor,  dilute  the  liquid  with  an  equal  volume  of  water, 
filter,  and  add  hydrochloric  acid  as  long  as  any  precipitate  is 


POTASSIUM    TART  RATE.  565 

formed.     This  precipitate   is  acid  tartrate  of  potassium,  which 
should  be  collected,  washed,  and  dried. 

Description. — Clear  colorless  crystals,  soluble  in  0.75  part  of 
water  at  15°,  and  in  0.50  part  of  boiling  water.  Odorless;  taste 
saline,  mildly  bitterish.  It  is  slightly  hygroscopic. 


SILVER;   PURE. 

ARGENTUM    PURUM. 

Ag=io8. 

Pure  or  sterling  silver  may  be  obtained  from  silversmiths. 
But  coined  silver,  and  the  silver  used  in  the  manufacture  of  silver- 
ware is  mixed  with  copper  to  harden  it.  This  alloy  can  be  puri- 
fied as  follows : 

The  silver  coin  or  old  silver  is  dissolved  in  nitric  acid  as  de- 
scribed under  the 'title  of  Argenti  Nitras;  the  solution  is  diluted 
with  distilled  water  and  filtered.  A  filtered  hot  solution  of  so- 
dium chloride  is  then  added  to  it  as  long  as  it  causes  precipita- 
tion. The  precipitated  silver  chloride  is  washed  with  boiling 
distilled  water  and  then  dried.  The  dried  chloride  is  thoroughly 
mixed  with  an  equal  weight  of  dry  potassium  carbonate,  and  the 
mixture  is  heated  in  a  clay  crucible,  first  at  a  low  red  heat  for 
about  half  an  hour,  or  until  the  silver  chloride  has  been  decom- 
posed, and  without  causing  the  mass  to  fuse;  after  which  the 
heat  is  increased  until  the  whole  contents  of  the  crucible  under- 
goes complete  fusion  so  that  the  metallic  silver  runs  together 
forming  a  button  or  lump. 

Crystallised  Silver. 

Silver 60  parts 

Nitric  acid  (68%  HNO3) 70  parts 

Water. 

Stronger  ammonia  water. 

Sodium  bisulphite. 

Dissolve  the  silver  in  the  acid  previously  diluted  with  100  parts 
of  water,  with  the  aid  of  gentle  heat,  in  the  fume  chamber. 
Evaporate  the  solution  to  dryness.  Heat  the  residue  in  a  por- 


566  SILVER. 

celain,  dish  until  it  fuses.  Continue  heating  until  the  fused  salt 
begins  to  turn  black.  Let  it  cool.  Dissolve  the  mass  in  150 
parts  of  water  and  filter  the  solution.  Add  ammonia  water,  stir- 
ring well,  until  the  liquid  acquires  a  decided  ammoniacal  odor. 

Make  a  forty  per  cent  solution  of  sodium  bisulphite  in  water 
and  filter.  Add  a  sufficient  quantity  of  this  solution  to  the  am- 
moniacal silver  solution  to  reduce  the  cupric  salt  in  the  latter  to 
the  cuprous  state.  This  may  be  known  to  have  been  accomplished 
when  a  sample  of  the  blue  liquid  becomes  decolorized  on  heating  it. 

Let  the  liquid  stand  in  a  cold  place  until  most  of  the  silver  has 
crystallized  out,  which  it  does  slowly.  Collect  the  crystals,  wash 
them  with  cold  distilled  water  and  then  cover  them  with  strong 
ammonia  water  and  let  stand  for  a  few  hours.  Wash  again  with 
distilled  water  and  then  dry. 

To  recover  the  remainder  of  the  silver  from  the  mother  liquor 
heat  it  at  from  60°  to  70°  until  all  of  the  metal  has  precipitated, 
and  wash  and  dry  this  precipitate  in  the  same  way  as  the  other. 


SILVER   CHLORIDE. 

ARGENTI    CHLORIDUM. 


Silver  nitrate  .........................    17  parts 

Sodium  chloride  .......................     6  parts 

Distilled  water. 

Dissolve  the  silver  nitrate  in  200  parts  of  distilled  water,  and 
the  sodium  chloride  in  100  parts.  Filter  both  solutions.  Heat 
the  sodium  chloride  solution  to  boiling.  Add  the  silver  solution 
to  that  of  the  sodium  chloride,  stirring  well.  Wash  the  precipi- 
tated silver  chloride  with  boiling  distilled  water  until  the  wash- 
ings are  perfectly  tasteless.  Dry  the  product  with  the  aid  of 
moderate  heat. 

Keep  it  in  dark  amber-colored  bottles. 

Reaction.     AgNO8+NaCl=AgCl+NaNO8. 

Description.  —  A  white,  heavy,  insoluble,  odorless  and  tasteless 
powder.  Readily  soluble  in  ammonia  water.  Darkened  by  light. 


SILVER  CYANIDE.  567 

SILVER   CYANIDE. 

ARGENTI    CYANIDUM. 

AgCy—  134. 

Silver  nitrate  .........................   34  parts 

Potassium    cyanide  ....................    13  parts 

Distilled  water. 

Dissolve  the  silver  nitrate  in  500  parts  and  the  potassium  cyanide 
in  200  parts  of  distilled  water.  Add  the  solution  of  potassium 
cyanide  to  the  solution  of  silver  nitrate,  gradually,  and  stir  well. 
Wash  the  precipitate  with  distilled  water,  and  dry  it  with  the  aid 
of  moderate  heat.  Keep  it  well  protected  against  light. 

Reaction.     AgNO3+KCy=AgCy+KNO8. 

Notes,  The  solution  of  silver  nitrate  might  advantageously  be 
acidulated  with  nitric  acid. 

Description.  —  A  heavy,  white,  odorless  and  tasteless  powder. 
Insoluble  in  water  or  alcohol.  Darkens  on  exposure  to  light. 

SILVER    IODIDE. 

ARGENTI    IODIDUM. 


Silver   nitrate  ...........................    I  part 

Potassium    iodide  .......................    I  part 

Dissolve  the  salts  separately,  each  in  about  12  parts  of  dis- 
tilled water.  Pour  the  solution  of  silver  nitrate  gradually  and 
with  constant  stirring  into  the  solution  of  the  iodide.  Collect  the 
precipitate  on  a  filter,  wash  it  well  with  distilled  water,  and  dry 
it  between  bibulous  paper. 

The  product  is  to  be  kept  in  well  closed  bottles  and  protected 
from  light. 

Reaction.     AgNO8+KI=AgI+KNO8. 

Description.  —  A  heavy,  light-yellowish  powder;  odorless  and 
tasteless.  Insoluble  in  water  and  alcohol. 


j 68  SILVER  NITRATE. 

SILVER    NITRATE. 

ARGENTI    NITRAS. 

AgN03=i7o. 

Silver   30  parts 

Nitric  acid  (containing  68%  of  HNO3) .  .   35  parts 
Distilled    water 50  parts 

Add  the  nitric  acid  and  the  water  to  the  metal  in  a  flask,  and 
heat  gently  until  dissolved.  Decant  the  clear  liquid  into  a  por- 
celain capsule,  evaporate,  and  set  aside  to  crystallize.  Let  the 
crystals  drain  in  a  glass  funnel,  and  dry  them  by  exposure  to  the 
hot  air,  carefully  avoiding  contact  with  organic  matter. 

Keep  it  in  an  amber  colored  bottle,  with  glass  stopper. 

Reaction.     3Ag+4HNO3=3AgNO3+2H2O+NO. 

Notes.  If  coin  is  used  it  should  be  well  cleaned  with  hot  soda 
solution  before  it  is  dissolved  in  the  acid. 

The  metal  dissolves  rapidly  at  first,  and  with  considerable 
evolution  of  heat.  Afterwards,  however,  the  reaction  is  slower 
as  the  solution  becomes  more  concentrated.  To  prevent  loss  by 
spurting,  the  neck  of  the  flask  may  be  covered  by  a  watch-crystal. 

When  large  quantities  are  operated  upon  the  flask  may  be  set 
in  a  warm  place  and  left  for  several  days.  The  clear  liquid  is 
then  decanted  from  the  residue,  and  the  latter  is  washed,  the 
filtered  washings  being  added  to  the  other  solution.  It  is  best 
to  have  the  metal  present  in  excess  so  that  a  small  quantity  of  it 
remains  undissolved.  By  this  precaution  vapors  of  nitric  acid  are 
avoided  in  the  subsequent  evaporation. 

To  remove  copper,  if  present,  the  solution  is  evaporated  to  dry- 
ness  and  the  mass  fused  in  a  thin  porcelain  capsule  (Meissen 
dish)  over  a  sand-bath,  keeping  the  salt  fused  two  or  three  hours 
until  a  small  quantity  of  it,  when  removed  from  the  dish,  dis- 
solved in  water,  and  the  solution  filtered,  is  not  turned  blue  by 
ammonia  water.  All  of  the  copper  nitrate  which  was  present  has 
now  been  reduced  to  cupric  oxide.  The  mass  is  then  poured  into 
a  clean  polished  iron  dish  or  mortar,  and  allowed  to  cool ;  it  can- 
not be  allowed  to  cool  in  the  porcelain  dish  for  that  will  burst. 


SILVER  NITRATE.  569 

The  salt  is  then  redissolved  in  distilled  water,  the  solution  is 
filtered,  and  crystallization  effected. 

Both  fused  and  crystallized  silver  nitrate  are  free  from  water. 

'In  evaporating  a  solution  of  silver  nitrate  to  crystallization 
sand-bath  heat  may  advantageously  be  employed  until  crystals 
begin  to  form.  Then  a  little  nitric  acid  should  be  added,  the 
dish  should  be  transferred  to  a  water-bath  and  evaporation  con- 
tinued until  a  sample  of  the  solution  solidifies  on  cooling.  The 
dish  is  then  put  in  a  dark  place  and  well  covered.  The  crystals 
are  to  be  drained  in  a  funnel,  and  then  dried  with  the  aid  of 
moderate  heat. 

The  mother  liquor  should  be  evaporated  to  dryness  to  recover 
all  of  the  silver  nitrate. 

Description. — Colorless,  transparent,  tabular  crystals ;  odorless  ; 
taste  bitter,  caustic,  nauseous,  strongly  metallic.  Darkens  on  ex- 
posure to  light  in  the  presence  of  organic  matter,  especially  if 
damp.  Soluble  at  15°  in  0.6  part  of  water,  and  in  o.i  part  of 
boiling  water.  Soluble  in  26  parts  of  alcohol  but  is  decomposed  in 
alcoholic  solution. 

Fused   Silver  Nitrate.     Lunar   Caustic.     Lapis   Inf emails.) 

Silver  nitrate 100  parts 

Hydrochloric   acid 4  parts 

Fuse  the  silver  nitrate  in  a  porcelain  capsule  on  a  sand-bath 
at  as  low  a  temperature  as  possible ;  then  add  the  acid  gradually, 
stirring  well,  and  when  nitrous  vapors  cease  to  be  evolved,  mould 
the  salt  into  sticks  or  cones  by  means  of  a  suitable  mould  of  bright 
polished  iron,  or  of  silver. 

Notes.  By  the  addition  of  hydrochloric  acid,  silver  chloride  is 
introduced  into  the  preparation:  AgNO3+HCl=:AgCl+HNO3. 
The  object  of  this  is  to  render  the  fused  sticks  more  tough  and 
strong. 

Silver  nitrate  fused  with  5  per  cent  of  potassium  chloride  is 
also  a  useful  toughened  caustic  containing  enough  silver  chloride 
and  potassium  nitrate  to  be  used  in  the  usual  sticks  or  pencils  with 
lessened  danger  of  breakage. 


57°  SILVER  NITRATE. 

Description. — A  heavy  opaque  solid,  usually  of  a  grayish  color ; 
fracture  granular  crystalline. 

About  95  per  cent  of  the  mass  is  readily  soluble  in  water.  The 
remaining  5  per  cent,  consisting  of  chloride,  is  not.  It  is  not  so 
quickly  soluble  as  the  pure  salt. 

Diluted  Silver  Nitrate. 

Silver  nitrate I  part 

Potassium    nitrate 2  parts 

Fuse  the  salts  together  in  a  porcelain  dish  over  a  sand-bath  at 
as  low  a  temperature  as  possible,  stirring  constantly  until  the 
mass  flows  quietly.  Then  cast  the  melted  mass  in  suitable  moulds. 

Notes.  Silver  nitrate  alone,  when  fused  and  moulded  into  pen- 
cils, is  too  brittle,  and  it  happens  frequently  that  a  less  energetic 
caustic  than  the  pure  silver  salt  is  desired.  Hence  the  pharma- 
copoeias prescribe  mixtures  of  silver  nitrate  and  potassium  nitrate, 
and  some  pharmacopoeias  contain  two  such  mixtures — one  consist- 
ing of  equal  parts,  and  another  of  one  part  silver  nitrate  and  two 
parts  of  potassium  nitrate.  The  Pharmacopoeia  of  the  United 
States  prescribes  equal  parts  in  the  Sixth  Revision  (1880),  but 
orders  the  more  diluted  kind  in  the  Seventh  Revision  (1890). 

Description. — A  hard  solid,  finely  crystalline,  and  readily 
soluble  in  water.  It  has  a  metallic  taste  and  caustic  properties 
similar  to  the  pure  nitrate. 

Mixtures  of  silver  nitrate  and  potassium  nitrate  in  other  pro- 
portions are  also  offered  by  manufacturers  of  chemicals,  and  dis- 
tinguished from  each  other  by  numbers. 

Silver  Nitrate  with  Lead. 

This  caustic  in  pencils  is  made  by  fusing  together  15  parts  of 
lead  nitrate  and  85  parts  of  silver  nitrate,  moulding  the  mixture 
into  sticks  of  the  usual  form.  It  is  recommended  as  preferable 
to  other  silver  nitrate  caustics  on  account  of  its  greater  toughness 
and  softness.  It  can  be  sharpened  to  a  point  with  the  knife,  like 
a  lead  pencil. 


SILVER  OLEATE.  57! 

SILVER   OLEATE. 

ARGENTI    OLEAS. 

AgC18H3302=  389. 

Crystallized  silver  nitrate  ................   25  Gm 

White  castile  soap,  in  fine  powder  .........  45  Gm 

Dissolve  the  silver  nitrate  in  1,500  ml  of  cold  distilled  water, 
and  the  soap  in  500  ml  of  hot  water.  Add  the  soap  solution  very 
slowly  and  with  brisk  stirring  to  the  silver  solution.  Collect  the 
oleate,  drain  it,  and  wash  it  several  times  with  cold  distilled  water. 
Dry  it  without  the  aid  of  heat,  protecting  it  from  exposure  to 
light  or  dust. 

Reaction.     AgNOs+NaC18H88O2=AgC18H38O2+NaNO,. 

Notes.  Silver  oleate  is  very  sensitive  to  light,  heat,  and  contact 
with  dust,  impure  air,  etc.  When  first  formed  it  is  nearly  white, 
but  cannot  be  kept  so  unless  it  is  prepared  at  night  or  in  a  dark 
room.  Decomposition  may  be  to  a  great  extent  prevented  by  sur- 
rounding and  covering  with  yellow  paper  the  funnel  in  which  the 
oleate  is  washed.  If  properly  precipitated  it  is  finely  granular, 
and  it  should  be  dried  by  the  use  of  white  blotting  paper,  fre- 
quently changed.  If  carefully  protected  the  product  will  be  of 
a  light  purplish  white  color. 

The  product  is  about  56  Gm,  containing  29.77  Per  cent  °f  silver 
oxide.  It  should  be  kept  in  small  amber  glass  stoppered  bottles, 
wrapped  in  yellow  paper. 

SILVER   OXIDE. 

ARGENTI    OXIDUM. 


Silver  nitrate  ..........  ...............     2  parts 

Distilled   water  ........................   40  parts 

Solution  of  potassium  hydroxide  ($%)••  .    13  parts 

Dissolve  the  silver  nitrate  in  the  water.     To  this  solution  add 
solution  of  potassa  so  long  as  any  precipitate  is  produced  by  it. 


572  SILVER  OXIDE. 

Wash  the  precipitate  with  distilled  .water  until  the  washings  are 
nearly  tasteless.  Dry  the  product  and  keep  it  well  protected  from 
the  light. 

Reaction.     2AgNO3+2KOH=Ag2O+2KNO3-fH2O. 

Notes.  Instead  of  potassium  hydroxide  a  corresponding 
amount  of  calcium  hydroxide  may  be  used.  The  proportions  re- 
quired are  then  I  part  of  silver  nitrate  dissolved  in  20  parts  of 
water,  and  135  parts  of  saturated  solution  of  calcium  hydroxide 
(lime  water). 

Silver  oxide  easily  parts  with  its  oxygen,  and  hence  must  not 
be  brought  in  contact  with  readily  oxidizable  substances,  as  ex- 
plosion may  result.  Moderate  heat  also  decomposes  it.  With 
ammonia  it  forms  a  violently  explosive  compound  known  as 
"fulminate  of  silver."  Great  care  is  accordingly  necessary  in 
handling  this  preparation.  It  should  be  kept  in  a  well-closed 
bottle  and  in  a  cool  place. 

Description. — A  heavy,  dark-brown,  nearly  black,  powder ;  odor- 
less ;  taste  metallic.  Nearly  insoluble  in  water  to  which  it,  never- 
the  less,  imparts  an  alkaline  reaction. 

SODIUM    ACETATE. 

SODII   ACETAS. 

NaC2H302.3H20=i36. 

Lead   acetate 20  parts 

Sodium    carbonate 15  parts 

Acetic  acid,  sufficient. 

Dissolve  the  salts,  each  in  sixty  parts  of  water ;  filter,  and  add 
the  solution  of  lead  acetate  to  that  of  the  sodium  carbonate,  stir- 
ring briskly.  Set  aside  to  settle.  Decant  the  supernatant  liquid ; 
wash  the  precipitate  with  a  little  cold  distilled  water  and  add  the 
washings  to  the  decanted  solution.  Filter.  Add  enough  acetic 
acid  to  the  filtrate  to  render  it  distinctly  acid  to  litmus  paper; 
then  evaporate  it  to  25  parts,  and  set  it  aside  to  cool  and  crystallize. 
Concentrate  the  mother  liquor  by  evaporation,  and  crystallize 
again. 

Must  be  kept  in  tightly  corked  bottles. 


SODIUM   ACETATE.  573 

Reaction. 

3(Pb(C2H302)2.3H20)+3(Na2C03.ioH20,)^ 

2PbCO3.Pb(OH)2+6(NaC2H3O2.3H2O)+2oH2O+CO2. 

The  salt  effloresces  on  exposure,  and  in  order  to  safely  dry  the 
crystals  it  is  important  that  the  temperature  should  not  exceed 
30°  C.  (86°  F.).  Still  better  is  it  to  dry  the  crystallized  salt  in  a 
strong  current  of  cold  air  produced  by  a  blower. 

Bye-product. — The  precipitated  lead  carbonate  should  be  fur- 
ther washed  until  the  washings  cease  to  give  an  alkaline  reaction 
to  test-paper,  and  should  then  be  dried. 

Another  Method. 

Acetic  acid  (36% ) 100  parts 

Sodium  carbonate 85  parts 

Water 100  parts 

Put  the  acetic  acid  and  water  in  a  porcelain  dish.  Add  the 
coarsely  powdered  or  crushed  sodium  carbonate  in  small  por- 
tions, stirring  after  each  addition  until  effervescence  ceases  before 
adding  another  portion.  When  all  of  the  sodium  carbonate  has 
been  added  heat  the  liquid  to  the  boiling  point.  Then  add 

Sodium   carbonate 2  or  3  parts 

as  may  be  required  to  render  the  solution  quite  neutral  to  test- 
paper,  or  only  faintly  acid.  Filter.  Evaporate  the  filtrate  until 
a  test-portion  when  cooled  gives  crystals.  Then  let  the  liquid 
stand  until  cold.  Collect,  drain,  and  dry  the  crystals. 

Reaction. 
Na2CO8+2HC2HaO2=2NaC2HsO2+H2O+COa. 

Notes.  When  the  solution  is  to  be  tested  as  to  its  reaction  on 
test-paper  the  portion  taken  for  this  test  should  be  first  diluted 
with  about  three  times  its  volume  of  water.  Should  the  liquid  be 
found  to  have  an  alkaline  reaction  more  acetic  acid  must  be  added 
(and  the  whole  well  mixed)  until  the  reaction  is  slightly  acid. 

The  crystals  must  be  dried  at  the  ordinary  temperature. 

When  acetic  acid  containing  empyreumatic  products  is  used, 


574  SODIUM   ACETATE. 

their  odor  comes  out  on  neutralizing  the  acid.  The  acetate 
should  then  be  carefully  heated  to  complete  fusion  at  a  tempera- 
ture of  about  300°  (and  not  exceeding  310°)  for  half  an  hour 
when  the  empyreumatic  substances  will  be  decomposed.  The  salt 
is  then  recrystallized. 

Description.  —  Colorless,  transparent  crystals;  odorless;  tasle 
saline,  cooling.  Efflorescent  in  warm  dry  air.  Soluble  in  1.4 
parts  of  water  and  in  30  parts  of  alcohol  at  15°  ;  in  half  its 
weight  of  boiling  water,  and  in  twice  its  weight  of  boiling  alcohol. 
The  salt  becomes  liquid  at  60°,  and  anhydrous  at  123°.  It  de- 
composes at  315°  C.  Its  water-solution  ($%)  turns  red  litmus 
paper  blue,  but  should  not  redden  phenolphtalein  paper.  If  it 
reddens  phenolphtalein  it  probably  contains  sodium  carbonate. 

SODIUM   ARSENATE. 

SODII   ARSENAS. 

Na2HAsO4.7H2O=3i2. 

Arsenous  oxide  .......................  20  pares 

Sodium  nitrate  ........................   17  parts 

Dried  sodium  carbonate  ................   1  1  parts 

Powder  these  substances  and  mix  them  intimately  by  tritura- 
tion.  Heat  the  mixture  in  a  large  covered  clay  crucible  at  a 
red  heat  until  effervescence  has  ceased,  and  complete  fusion  takes 
place.  Let  the  fused  mass  solidify  on  a  porcelain  surface,  and, 
while  still  warm,  put  it  into  85  parts  of  boiling  distilled  water,  and 
stir  until  dissolved.  Filter  while  hot,  and  set  aside  to  crystallize. 
Collect,  drain,  and  dry  the  crystals,  and  keep  them  in  a  tightly 
corked  bottle. 

Reaction. 

As2O3+2NaNO3+Na2CO3=Na4As2O7+N2O3+CO2  ;  and, 
Na4As2O7+  1  5H2O=2  (  Na2HAsO47H2O  )  . 


Notes.  The  residue  after  the  process  of  heating  the  mixture 
is  sodium  pyroarsenate,  which  is  converted  into  orthoarsenate  by 
water. 


SODIUM  ARSENATE.  575 

When  crystallized  at  a  low  temperature  sodium  arsenate  has 
12  molecules  of  water  of  crystallization ;  at  ordinary  temperature 
it  usually  crystallizes  with  7H2O ;  in  dry  air  it  effloresces,  losing 
5H2O ;  the  last  of  the  water  is  driven  off  at  about  149°  C,  and 
when  heated  to  redness  it  becomes  converted  into  pyroarsenate, 
which,  however,  when  dissolved  in  water  becomes  immediately 
converted  back  into  arsenate. 

Description. — Colorless,  transparent,  odorless  crystals,  of  mild 
alkaline  taste  (very  poisonous).  Hygroscopic  in  moist  air. 
Soluble  in  4  parts  of  water  at  15°,  and  freely  soluble  in  boiling- 
water.  Very  sparingly  soluble  in  cold  alcohol;  soluble  in  60 
parts  of  boiling  alcohol. 

Solution  of  Sodium  Arsenate;  U.  S. 

Sodium  arsenate,  dried  at  149°  C I  part 

Distilled   water 99  parts 

Notes.  Owing  to  the  variable  amount  of  water  of  crystalliza- 
tion found  in  the  sodium  arsenate  of  commerce,  the  Pharma- 
copoeia directs  that  the  salt  should  be  heated  at  149°  C.  (300°  F.) 
until  deprived  of  all  its  water  of  crystallization  before  it  is 
weighed  out,  and  used  in  making  the  official  solution.  See  pre- 
ceding paragraph. 

SODIUM    BENZOATE. 

SODII    BENZOAS. 

502= 144- 

Benzoic  acid 40  parts 

Sodium  bicarbonate 28  parts 

Boiling   water 80  parts 

Mix  the  bezoic  acid  with  the  hot  water,  stir  well,  neutralize 
perfectly  by  adding  the  sodium  bicarbonate,  being  careful  to  ob- 
serve the  reaction  on  litmus  paper  after  effervescence  has  ceased. 
Filter.  Evaporate  to  55  parts ;  remove  it  from  the  source  of  heat 
and  stir  until  cold.  During  the  evaporation  it  is  necessary  to 
scrape  down  the  benzoate  from  the  sides  of  the  capsule. 

Reaction.     2HC7H,O2-hNa2CO,=-2NaC7H5O,-fH.O+CO2. 


5/6  SODIUM   BENZOATE. 

Description. — A  white,  semi-crystalline  or  amorphous  powder, 
efflorescent  on  exposure  to  air,  odorless  or  having  a  faint  odor 
of  benzoin,  of  a  sweetly  astringent  taste  free  from  bitterness,  and 
having  a  neutral  reaction.  Soluble  in  1.8  parts  of  water,  and  in 
45  parts  of  alcohol  at  15°  C. ;  in  1.3  parts  of  boiling  water,  and  in 
20  parts  of  boiling  alcohol. 


SODIUM    BICARBONATE. 

SODII     BICARBONAS. 

NaHCO3=84. 

Prepared  by  saturating  a  solution  of  sodium  carbonate  with 
carbonic  acid  gas,  or  by  conducting  carbonic  acid  gas  for  several 
days  into  closed  chambers  filled  with  crystallized  sodium  car- 
bonate. The  liberated  water  of  crystallization  retains  in  solution 
the  chloride  and  sulphate  which  may  have  been  present  in  the 
carbonate. 

It  may  also  be  prepared  as  follows : 

Stronger  ammonia  water  (28%  of  H3N)  .   250  Gm 

Sodium  chloride 250  Gm 

Water, 
Carbon  dioxide. 

Put  the  ammonia  solution  in  a  flask  of  2000  Cc.  capacity.  Add 
one  liter  of  water.  Pass  carbon  dioxide  into  the  mixture  until 
saturated,  keeping  the  flask  cool  by  means  of  a  stream  of  cold 
water. 

Dissolve  the  sodium  chloride  in  800  Gm  of  water  at  15°.  Add 
to  this  the  cold  solution  of  ammonium  bicarbonate,  stirring  well," 
and  continuing  the  addition  so  long  as  a  precipitate  is  formed. 
When  no  further  precipitation  results  from  the  addition  of  more 
of  the  solution  of  ammonium  bicarbonate,  collect  the  precipitated 
sodium  bicarbonate,  wash  it  with  some  cold  water  on  a  funnel,  and 
dry  it. 

Reactions.  HaN+H2O+CO2=H4NHCO3;  then  H,NHCO3+ 
NaCl=NaHCO8+H4NCl. 

Notes.     Ammonium  bicarbonate  is  not  freely  soluble  in  water. 


SODIUM    BICARBONATE.  577 

Should  any  separation  of  this  salt  occur  while  carbon  dioxide  is 
led  into  the  ammonia  water,  a  little  more  water  must  be  added  at 
the  close  of  that  part  of  the  process  to  redissolve  the  ammonium 
bicarbonate  thus  precipitated,  before  the  liquid  is  added  to  the 
solution  of  sodium  chloride. 

Purification.  Sodium  bicarbonate,  as  found  in  commerce,  is 
frequently  impure  from  chlorides  and  sulphates.  These  impuri- 
ties may  be  removed  by  washing  with  cold  distilled  water. 

Close  the  throat  of  a  glass  funnel  loosely  with  cotton.  Fill  the 
funnel  about  two-thirds  full  of  the  dry  powdered  commercial 
sodium  bicarbonate.  Cover  the  leveled  surface  of  the  salt  with 
a  disc  of  filter  paper.  Now  pour  upon  the  covered  salt  small 
quantities  of  cold  distilled  water,  about  30  to  50  Gm  at  a  time, 
and  let  the  water  percolate  through  the  salt.  After  a  quantity  of 
water  equal  to  rather  more  than  half  the  weight  of  the  sodium 
bicarbonate  has  passed  through,  test  the  washings  for  chlorides 
and  sulphates  in  the  usual  way.  When  the  washings,  acidified 
with  nitric  acid,  no  longer  become  turbid  on  the  addition  of  test- 
solution  of  either  silver  nitrate  or  barium  chloride,  dry  the  washed 
salt  with  the  aid  of  very  moderate  heat. 

Description. — A  white,  odorless  powder,  of  cooling,  mildly  alka- 
line taste.  Soluble  in  11.3  parts  of  water  at  15°.  Above  that 
temperature  the  salt  begins  to  lose  carbon  dioxide,  and  at  the  boil- 
ing point  of  water  it  is  converted  into  normal  carbonate  almost 
completely.  At  a  low  red  heat  it  is  completely  converted  into 
normal  carbonate. 

Insoluble  in  alcohol  and  in  ether. 


Vichy  Salt. 

Sodium  bicarbonate 85  parts 

Sodium  chloride 5  parts 

Sodium  sulphate    9  parts 

Potassium  carbonate i  part 

Mix  the  separately  powdered  dry  ingredients. 

11—37 


SODIUM  BISULPHITE. 

SODIUM     BISULPHITE. 

SODII    BISULPHIS. 

NaHSO3=i04. 

Prepared  by  saturating  a  solution  of  sodium  carbonate  with 
sulphur  dioxide  and  evaporating  the  solution  to  dryness. 

Must  be  kept  in  small,  entirely  filled,  tightly-closed  bottles,  in  a 
cool  place. 

Description. — Opaque  crystals  or  a  white,  granular  powder, 
emitting  a  sulphurous  odor ;  taste  disagreeable,  sulphurous.  Oxi- 
dized by  contact  with  air  to  sulphate,  giving  off  sulphur  dioxide. 
Soluble  at  15°  in  4  parts  of  water  and  in  72  parts  of  alcohol;  in 
about  2  parts  of  boiling  water  and  in  49  parts  of  boiling  alcohol. 
Its  water-solution  exhibits  an  acid  reaction  on  litmus  paper. 

SODIUM   BITARTRATE. 

SODII     BITARTRAS. 

NaHC4H406.H20=i9o. 

Tartaric  acid    20  parts 

Sodium  carbonate 19  parts 

Dissolve  one-half  of  the  acid  in  50  parts  of  distilled  water,  neu- 
tralize with  the  sodium  carbonate  and  filter.  Dissolve  the  other 
half  of  the  tartaric  acid  in  50  parts  of  distilled  water  and  filter. 
Mix  the  two  liquids.  Set  the  mixture  aside  in  a  cool  place  for  a 
day  or  two ;  then  collect  and  dry  the  precipitated  crystalline  salt. 

Description. — A  white,  crystalline  powder,  or  colorless  crystals  ; 
odorless;  acid  taste.  Sparingly  soluble  in  cold  water.  Insoluble 
in  alcohol. 

SODIUM    BROMIDE. 

SODII     BROMIDUM. 

NaBr— 103. 

Iron  wire,  cut 8  parts 

Bromine    24  parts 

Sodium  carbonate    45  parts 

Distilled  water,  sufficient. 


SODIUM    BROMIDE.  579 

Digest  the  iron  and  18  parts  of  bromine  with  50  parts  of  water 
in  a  flask  until  all  odor  of  bromine  has  ceased,  and  the  liquid  be- 
comes green.  Filter,  add  the  remainder  of  the  bromine  to  the 
filtrate,  and  let  it  dissolve. 

Dissolve  the  sodium  carbonate  in  100  parts  of  boiling  distilled 
water,  and  add  the  solution  of  bromide  of  iron.  Boil  for  fifteen 
minutes,  filter,  and  evaporate  the  filtrate  to  dryness  during  con- 
stant stirring. 

Notes.  The  reactions  are  analogous  to  those  occurring  in  the 
preparation  of  potassium  bromide  from  bromide  of  iron  and  potas- 
sium carbonate. 

The  sodium  bromide  may  also  be  made  from  bromine  and  solu- 
tion of  sodium  hydroxide,  as  potassium  bromide  is  prepared  from 
bromine  and  solution  of  potassium  hydroxide. 

See  also  notes  under  Potassium  Bromide. 

Where  the  salt  is  deposited  from  hot  concentrated  solutions  the 
crystals  are  anhydrous  and  cubical,  while  hydrated  monoclinic 
crystals  are  deposited  by  slow  evaporation  of  cold  solutions. 

Description. — Colorless  or  white  crystals,  or  a  white  granular 
salt ;  odorless ;  taste  saline,  slightly  bitter.  Somewhat  hygroscopic. 
Soluble  at  15°  in  1.2  parts  of  water  and  in  13  parts  of  alcohol ;  in 
half  its  weight  of  boiling  water,  and  in  1 1  parts  of  boiling  alcohol. 
The  water-solution  should  be  neutral  or  only  faintly  alkaline  to 
test-paper. 

SODIUM   CARBONATE. 

SODII     CARBONAS. 

Na2CO3.ioH2O=286. 

By  far  the  greater  portion  of  sal  sodae,  or  crude  sodium  car- 
bonate, consumed  at  this  time  is  prepared  by  the  so-called  Lc- 
blanc's  method.  A  mixture  of  sodium  sulphate,  chalk  and  coal 
is  strongly  heated  in  a  reverberatory  furnace;  the  mass  is  then 
leached  out  with  water,  the  solution  concentrated,  and  the  car- 
bonate, collected  as  it  separates  from  the  hot  liquid.  The  product 
contains  carbonate,  sulphide,  hydrate,  sulphate,  and  hyposulphite 


580  SODIUM    CARBONATE. 

of  sodium.  The  residue  obtained  by  evaporating  the  first  solution 
to  dryness  is  called  soda-ash,  of  which  several  hundred  million 
pounds  are  annually  imported  into  the  United  States.  The  crude 
sodium  carbonate  is  purified  by  re-crystallization. 

At  Natrona,  Pa.,  near  Pittsburg,  large  quantities  of  soda  are 
made  from  cryolite,  a  mineral  composed  of  the  fluorides  of  sodium 
and  aluminum.  A  mixture  of  powdered  cryolite  and  chalk  is  ig- 
nited in  a  furnace,  the  first  reaction  being:  6NaFl.Al2Fl6-j- 
6CaCOa=NaeO6Al2+6CaFl2+6CO2.  The  fused  mass  is  pow- 
dered and  the  sodium  aluminate  leached  out  by  water.  A  stream 
of  carbonic  oxide  is  conducted  through  the  solution  of  sodium 
aluminate,  which  produces  sodium  carbonate  and  aluminium  hy- 
drate: Na606Al2+3C02+3H20=3Na2C03+Al2(OH)G. 

A  third  method  consists  in  treating  a  solution  of  sodium  chloride 
with  NH3  and  afterwards  with  CO2 ;  the  ammonium  bicarbonate 
gives,  with  the  NaCl,  sodium  bicarbonate  and  NH4C1.  The  so- 
dium bicarbonate  is  then  converted  into  carbonate  by  heat,  after 
which  the  product  is  dissolved  and  crystallized. 

Both  the  ammonia  process  and  the  cryolite  process  yield  purer 
products  than  the  sodium  carbonate  made  by  Leblanc's  process. 

Uses.  Vast  quantities  of  sal  sodse  are  used  in  the  arts  and  man- 
ufactures and  in  the  household  economy.  In  pharmacy  it  is  used 
in  the  preparation  of  various  carbonates,  and  for  the  production 
of  sodium  compounds. 

Purification.  Commercial  sodium  carbonate  ("sal  sodse")  may 
be  purified  by  recrystallization,  as  follows : 

Soda  ash 4  parts 

Water    9  parts 

Mix  and  heat  to  80°  until  the  soda  ash  is  dissolved.  Filter. 
Evaporate  the  filtrate  to  a  density  of  1.25.  Let  the  liquid  slowly 
cool  to  about  12°.  Collect  the  crystals,  drain,  and  dry  them,  and 
place  them  in  a  dry  bottle. 

Additional  crops  of  crystals  are  to  be  recovered  from  the  mother- 
liquor  on  evaporation. 

Notes.     To  prevent  the  formation  of  lumps  the  soda  ash,  in 


SODIUM    CARBONATE.  581 

powder,  should  be  added  gradually  to  the  water,  stirring  con- 
stantly. 

Should  the  product  be  found  to  contain  sulphates  or  chlorides, 
or  both,  it  must  be  re-crystallized  several  times,  as  follows : 

Re  crystallization. 

Washing  soda   2  parts 

Water    3  parts 

Heat  the  water  to  about  40°  C,  and  dissolve  the  soda  in  it. 
Filter  the  solution,  and  set  it  in  a  crystallizer  that  crystals  may 
form  by  the  spontaneous  evaporation  of  the  water  at  the  ordinary 
room  temperature.  Collect  and  drain  the  crystals,  press  them 
gently  between  cloths  or  bibulous  paper,  dry  hastily,  put  the 
product  in  dry  bottles  and  close  tightly. 

Preparation  of  Pure  Sodium  Carbonate. 

It  may  be  made  by  heating  pure  sodium  bicarbonate  in  a  silver 
dish  at  low  red  heat  until  converted  into  normal  carbonate,  dis- 
solving the  mass  in  hot  water,  filtering,  and  crystallizing. 

The  preparation  of  purified  sodium  bicarbonate  is  described 
under  that  title. 

Another  Method. 

Sal  sodse 145  parts 

Oxalic  acid 60  parts 

Water. 

Dissolve  the  sal  sodse  in  100  parts  of  hot  water  and  the  oxalic 
acid  in  another  equal  amount  of  the  same  solvent.  Mix  the  solu- 
tion. Let  cool.  Collect  the  sodium  oxalate,  wash  it  with  500  parts 
of  cold  distilled  water  on  a  funnel,  drain,  and  dry.  Heat  to  low 
red  heat  until  the  oxalate  is  decomposed.  Dissolve,  filter,  and 
crystallize. 

Description. — Sodium  carbonate  consists  of  large,  transparent, 
colorless  crystals ;  odorless ;  taste  strongly  alkaline.  Efflorescent 
in  dry  air.  Soluble  in  1.6  parts  of  water  at  15°,  in  0.09  part  at 
38°,  and  in  0.2  part  of  boiling  water.  Insoluble  in  alcohol  and  in 
ether.  Soluble  in  1.02  parts  of  glycerin.  Dissolves  in  its  own 
water  of  crystallization  at  32°. 5,  and  begins  to  lose  some  of  that 
water.  The  water-solution  has  a  strongly  alkaline  reaction. 


582  SODIUM    CARBONATE. 

Dried  Sodium  Carbonate. 
Na2CO:5.2H2O. 

Expose  crystallized  sodium  carbonate  in  small  fragments  or 
crystals,  for  several  days,  to  a  temperature  not  exceeding  25° 
until  completely  effloresced;  then  dry  it  at  not  over  45°  until  re- 
duced to  one-half  the  weight  of  the  crystallized  salt  originally 
taken. 

Triturate  the  product  in  a  mortar  until  a  uniform  powder  is 
obtained  and  keep  this  in  well-closed  bottles. 

Notes.  Crystallized  sodium  carbonate  contains  10  molecules  of 
water  of  crystallization.  When  exposed  to  the  air  it  effloresces, 
and  in  the  course  of  one  or  more  weeks,  according  to  the  tempera- 
ture and  dryness  of  the  air,  it  loses  about  40  per  cent  of  its  weight. 
At  45°  C.  it  loses  all  but  2  molecules  of  its  water  of  crystallization. 
[At  90°  to  100°  C.  it  becomes  anhydrous.] 

At  about  32.°  5  crystallized  sodium  carbonate  dissolves  in  its 
water  of  crystallization.  This  "aqueous  fusion"  should  be  avoided 
in  the  preparation  of  dried  sodium  carbonate  because  it  renders  the 
subsequent  completion  of  the  process  more  difficult.  It  is,  there- 
fore, directed  that  the  crystallized  salt  shall  be  effloresced  at  from 
20°  to  25°  C.  before  higher  heat  is  applied. 

Description. — A  white,  amorphous  powder. 
SODIUM    CHLORATE. 

SODII    CHLORAS. 

NaClO3= 106.25. 

Prepared  from  calcium  hydroxide  and  sodium  chloride  with 
chlorine,  or  from  chlorinated  lime  and  sodium  chloride,  by  a 
process  analogous  to  that  for  preparing  potassium  chlorate. 

It  may  also  be  made  as  follows : 

Tartaric  acid    117  parts 

Sodium  carbonate   no  parts 

Potassium  chlorate 96  parts 

Dissolve  the  acid  and  the  carbonate  in  1000  parts  of  hot  water. 


SODIUM   CHLORATE.  583 

To  the  hot  solution  add  the  potassium  chlorate.  Potassium  bitar- 
trate  separates,  and  the  solution  contains  the  sodium  chlorate  to- 
gether with  some  potassium  bitartrate,  which  deposits  during  the 
evaporation  to  crystallization,  the  last  being  gotten  rid  of  by 
crystallizing  it  out  from  the  saturated  solution  of  the  sodium 
chlorate. 

Description. — Colorless  transparent  crystals,  or  a  white  crystal- 
line powder;  odorless;  taste  saline,  cooling.  Soluble  at  15°  in  i.i 
parts  of  water,  and  in  about  100  parts  of  alcohol ;  in  half  its  weight 
of  boiling  water  and  in  40  parts  of  boiling  alcohol ;  in  5  parts  of 
glycerin.  The  water-solution  is  neutral  to  test-paper.  Like  potas- 
sium chlorate  the  sodium  chlorate  must  be  handled  with  care,  and 
not  triturated  with  reducing  agents  or  subjected  to  concussion. 

SODIUM   CHLORIDE. 

SODII      CHLORIDUM. 

NaCl=s8.4. 

Diluted  hydrochloric  acid 5  parts 

Sodium  carbonate   2  parts 

Add  the  sodium  carbonate  gradually  to  the  diluted  acid.  Make 
the  solution  quite  neutral  to  litmus  paper.  Filter.  Evaporate  to 
dryness,  or  to  crystallization,  as  may  be  desired. 

Reaction.    Na2CO3+2HCl=2NaCl+H,O+CO2. 

Purification  of  Common  Salt. 

Common  salt I     kilogram 

Water    3^  liters 

Lime    12     Gm 

Barium  chloride, 
Sodium  carbonate, 
Hydrochloric  acid. 

Dissolve  the  salt  in  the  water.  Slake  the  lime,  mix  it  with  100 
ml  of  water,  and  add  the  mixture  to  the  salt  solution.  Heat  to  the 
boiling  point.  Filter.  Add  a  solution  of  barium  chloride  to  the 
filtrate  as  long  as  it  causes  precipitation.  Then  add  solution  of 
sodium  carbonate  until  all  the  calcium  and  barium  shall  have  been 


584  SODIUM   CHLORIDE. 

separated.    Filter.    Neutralize  with  hydrochloric  acid.    Evaporate 
to  crystallization  or  granulation,  and  dry  the  salt  thoroughly. 

Notes.  Common  salt  contains  magnesium  and  calcium  salts 
(chlorides  and  sulphates).  These  are  precipitated  as  described. 

Description. — Colorless  crystals  or  a  white,  granular  crystalline 
powder ;  dry ;  odorless,  and  of  purely  saline  taste.  Not  hygro- 
scopic. Soluble  in  2.8  parts  of  water  at  15°,  and  in  2.5  parts  at 
100°.  Almost  insoluble  in  alcohol.  The  water-solution  is  neutral 
to  litmus  paper. 

Kissing  en  Salt. 

Dried  sodium  sulphate 90  parts 

Precipitated  calcium  sulphate 50  parts 

Potassium  sulphate   1 1  parts 

Ferrous  sulphate   3  parts 

Sodium  bicarbonate    170  parts 

Dried  magnesium  sulphate 130  parts 

Sodium  chloride    400  parts 

Tartaric  acid    10  parts 

Mix  the  separately  powdered  dry  ingredients  well. 


SODIUM    CITRATE    SOLUTION. 

LIQUOR    SODII    CITRATIS. 

A  solution  of  normal  sodium  citrate  of  which  each  milliliter 
contains  0.50  Gm  of  Na3C6H5O7  is  prepared  as  follows : 

Citric  acid 400  Gm 

Sodium   bicarbonate 486  Gm 

Dissolve  the  sodium  bicarbonate  in  750  ml  of  distilled  water  by 
the  aid  of  heat,  gradually  add  the  citric  acid,  and,  when  efferves- 
cence has  ceased,  bring  the  liquid  to  the  boiling  point.  If  the  so- 
lution is  not  neutral  to  litmus  paper,  add  more  sodium  bicar- 
bonate (or  citric  acid,  as  the  case  may  require)  to  produce  a 
perfectly  neutral  reaction.  Finally,  add  enough  distilled  water 
to  make  the  whole  measure  1080  ml. 

To  make  solution  of  di-sodium-hydrogen  citrate,    containing 


SODIUM  CITRATE.  585 

0.50  Gm  of  Na2HC6H5O7  in  each  ml  add  200  Gm  of  citric  acid  to 
1080  ml  of  the  above  solution,  and  finally  add  enough  distilled 
water  to  make  the  whole  product  measure  1480  ml. 
Used  in  making  certain  scale  salts  of  iron. 

Potio  Riveri 

is  a  preparation  of  the  German  Pharmacopceia  made  of  4  parts 
of  citric  acid,  190  parts  of  water  and  9  parts  of  sodium  carbonate 
in  crystals.  It  is  directed  to  be  freshly  prepared  whenever  pre- 
scribed. 

SODIUM    ETHYLSULPHATE. 

SODII    ET   AETHYL    SULPHAS'. 

[Sodium  Sulphovinate.] 
NaC2HBSO4.H2O=i66. 

Alcohol    -5  parts 

Sulphuric  acid 5  parts 

Barium  carbonate 10  parts 

Sodium  carbonate 3  parts 

Put  the  alcohol  in  a  large  porcelain  dish,  and  set  it  in  rapid  ro- 
tary motion  by  stirring  with  a  glass  rod.  Add  the  sulphuric  acid 
in  a  small  stream.  Pour  the  cooled  mixture  into  a  bottle  and 
close  it  with  a  glass  stopper.  Let  it  stand  over  night.  Pour  it 
back  into  the  porcelain  dish.  Add  gradually,  and  with  constant 
and  vigorous  stirring,  the  powdered  barium  carbonate,  previ- 
ously sifted  so  as  to  be  free  from  lumps.  After  all  the  barium 
carbonate  has  been  added  return  the  mixture  to  the  bottle  and 
shake  well.  Filter  the  liquid.  Then  add  to  it,  in  small  portions 
at  a  time,  the  sodium  carbonate  until  no  further  precipitation  oc- 
curs on  the  addition  of  more.  [Filter  a  small  portion  of  the  liquid 
before  all  of  the  sodium  carbonate  has  been  added,  and  test  it  by 
further  addition  of  sodium  carbonate  to  determine  how  much 
more  of  the  alkali  carbonate  is  required  to  precipitate  the  barium.] 
When  all  the  barium  has  been  precipitated  [without  using  an 
excess  of  sodium  carbonate] ,  filter  the  solution  and  evaporate  the 
filtrate  with  the  aid  of  moderate  heat  to  crvstallization. 


586  SODIUM    ETHYLSULPHATE. 

Description. — Colorless  laminar  crystals,  somewhat  efflorescent ; 
readily  soluble  in  water. 

Solution  of  Sodium  Ethylate;  B.  P. 
An  alcoholic  solution  containing  18  per  cent  of  C2H5ONa. 

Sodium,  clean  and  bright I  Gm 

Absolute  alcohol 20  ml 

Cautiously  dissolve  the  sodium  in  the  alcohol  in  a  flask  kept 
cool  by  flowing  water. 

Reaction.     2C2HBOH+Na2=2C2HBONa+H2. 

Notes.  The  metal  should,  if  larger  quantities  be  employed,  be 
added  gradually.  The  heat  liberated  by  the  reaction  is  great, 
and  hence  the  liquid  must  be  kept  cold. 

Description. — A  colorless  syrupy  liquid  which  becomes  brown 
on  keeping.  It  must  be  freshly  prepared  when  required. 
Sp.  w.  0.867. 

SODIUM    HYDROXIDE. 

SODII    HYDROXIDUM. 

NaOH=40. 

Prepared  by  evaporating  the  solution  of  sodium  hydroxide  to 
dryness,  fusing  the  residue,  dissolving  it  in  alcohol,  which  leaves 
carbonate  undissolved,  after  which  the  alcohol  is  distilled  off  from 
the  clear  solution  and  the  sodium  hydroxide  again  fused. 

This  alkali  must  be  preserved  in  the  same  manner  as  potassium 
hydroxide — in  tightly  closed  bottles  of  hard  green  glass,  the 
stoppers  to  be  rubbed  with  a  little  petrolatum  to  prevent  them 
from  being  cemented  into  the  necks  of  the  bottles. 

Description. — Dry,  white,  translucent,  hard,  of  crystalline  frac- 
ture, odorless,  acrid,  caustic,  corrosive.  Hygroscopic,  but  not 
deliquescent,  becoming  first  moist  and  then  converted  into  dry  car- 
bonate on  exposure  to  air.  Soluble  in  1.7  parts  of  water  at  15°, 
and  in  0.8  part  of  boiling  water.  Freely  soluble  in  alcohol. 
Strongly  alkaline. 


SODIUM   HYDROXIDE.  587 

SODIUM    HYDROXIDE    SOLUTION. 

LIQUOR    SODII    HYDROXIDI. 

[Liquor  Sodse;  U.S.] 

An  aqueous  solution  containing  5  per  cent  of  sodium  hydroxide. 
NaOH=40. 

Sodium  carbonate 17  parts 

Calcium   oxide 5  parts 

Distilled  water,  sufficient. 

Dissolve  the  sodium  carbonate  in  40  parts  of  boiling  distilled 
water.  Slake  the  lime  and  make  of  it  a  smooth  mixture  with 
40  parts  of  distilled  water  and  heat  this  mixture  to  boiling.  Then 
add  gradually  the  sodium  carbonate  solution  to  the  "milk  of 
lime,"  and  boil  the  whole  mixture  for  ten  minutes.  Remove  the 
heat,  cover  the  vessel  tightly,  and,  when  the  contents  are  cold, 
add  enough  distilled  water  to  make  the  whole  weigh  100  parts. 
Lastly  strain  the  liquid  through  linen,  or,  when  the  precipitate 
has  subsided,  draw  off  the  clear  solution  by  means  of  a  syphon. 

Reaction.     Na2CO3+Ca(OH)2==2NaOH+CaCO3. 

Notes.  The  sodium  carbonate  employed  must,  of  course,  be  the 
crystallized  salt,  not  in  any  degree  effloresced. 

The  lime  might  advantageously  be  washed  free  from  dust  and 
salts  before  being  used.  This  is  done  as  follows :  Slake  the  5  parts 
of  lime  with  about  40  parts  of  water ;  then  add  about  500  parts  of 
water  and  stir  the  mixture  occasionally  during  half  an  hour ;  let 
the  calcium  hydroxide  subside,  decant  the  liquid  and  throw  this 
away.  Then  add  40  parts  of  pure  water,  heat  to  boiling  and  use 
this  liquid  with  the  solution  of  sodium  carbonate  as  described 
in  the  formula  above  given. 

A  considerable  excess  of  lime  is  used,  but  as  calcium  hydroxide 
is  insoluble  in  a  solution  of  sodium  hydroxide  no  lime  will  be 
contained  in  the  product.  An  unnecessarily  large  excess  of  lime 
is,  however,  objectionable  because  the  superfluous  calcium  hy- 
droxide does  not  subside  as  readily  as  the  calcium  carbonate. 

If  cold  liquids  are  used  the  calcium  carbonate  formed  by  the 
reaction  is  so  finely  divided  and  light  that  it  subsides  very  slowly 


588  SODIUM   HYDROXIDE. 

and  the  bulky  precipitate  retains  much  liquid  causing  correspond- 
ing loss  of  product. 

More  concentrated  solutions  can  not  be  used  because  the  reac- 
tion will  not  then  be  complete.  It  is  completed  when  the  liquid 
no  longer  effervesces  with  dilute  acid  or  when  it  does  not  cause 
turbidity  when  dropped  into  a  clear  solution  of  calcium  hydroxide. 

Solution  of  sodium  hydroxide  is  usually  clarified  by  subsidence 
and  decantation ;  but  it  may,  if  preferred,  be  successfully  filtered 
through  coarsely  powdered  and  washed  marble. 

The  strength  of  such  a  preparation  as  solution  of  sodium  hy- 
droxide should  not  be  fixed  by  the  quantities  and  proportions  of 
the  materials  as  is  done  in  the  Pharmacopoeia  from  which  the 
foregoing  formula  is  borrowed ;  it  should  be  tested  quantitatively 
with  volumetric  solution  of  sulphuric  acid  and  the  strength  ad- 
justed by  dilution  in  accordance  with  the  result.  In  order  to  carry 
out  this  plan  the  quantity  of  water  used  in  the  process  may  be 
diminished  ten  per  cent  and  the  product  diluted  as  required ;  or 
the  amount  of  water  directed  may  be  used  and  the  product  di- 
luted, or  concentrated  by  evaporation,  as  may  be  found  necessary. 

Solution  of  sodium  hydroxide  attacks  organic  matter  ener- 
getically and  is  therefore  discolored  by  contact  with  organic  sub- 
stances. It  also  attacks  ordinary  flint  glass  so  that  if  it  be  put 
in  glass-stoppered  bottles  of  that  kind  of  glass  the  stoppers 
usually  become  firmly  fixed  and  can  not  be  removed,  necessitating 
the  breaking  of  the  bottles  to  get  at  the  contents.  The  solution 
should,  therefore,  be  kept  in  bottles  made  of  green  glass  which 
is  not  so  easily  attacked  by  the  alkali,  and  the  stoppers  should 
be  coated  with  a  little  paraffin  or  petrolatum. 

Description. — The  official  sodium  hydroxide  solution  is  a  clear, 
colorless  and  odorless  liquid,  having  a  very  acrid  and  caustic  taste, 
a  corrosive  action  on  organic  matter,  and  a  strongly  alkaline 
reaction. 

Its  specific  weight  is  about  1.059,  and  the  specific  volume  0.944. 

Valuation.  To  neutralize  20  Gm  of  official  solution  of  sodium 
hydroxide  should  require  25  ml  of  normal  sulphuric  acid,  each  ml 
of  the  test  solution  indicating  0.2  per  cent  of  NaOH ;  phenolphta- 
lein  should  be  used  as  indicator. 

One  ml  of  normal  sulphuric  acid  is  the  equivalent  of  0.03996 
Gm  of  NaOH. 


SODIUM     HYPOCHLORITE.  589 

SODIUM    HYPOCHLORITE    SOLUTION. 

LIQUOR    SODAE    CHLORATAE. 

[Labarraque's  Solution.] 

An  aqueous  solution  containing  sodium  hypochlorite  as  its  most 
important  constituent.  The  Pharmacopoeia  requires  that  the 
preparation  shall  furnish  at  least  2.6  per  cent  of  available 
chlorine. 

Sodium  carbonate 30  parts 

Chlorinated   lime 15  parts 

Water,  sufficient. 

Triturate  the  chlorinated  lime  with  40  parts  of  water,  produc- 
ing a  uniform  mixture.  Let  the  heavier  particles  subside  and 
transfer  the  liquid  to  a  filter.  Treat  the  undissolved  solid  mat- 
ter with  35  parts  of  water  and  add  this  mixture  to  the  first,  pass- 
ing the  whole  through  the  filter.  Wash  the  filter  and  contents 
with  20  parts  of  water,  letting  this  portion  also  pass  through 
the  filter  and  be  added  to  the  previous  solutions. 

Dissolve  the  sodium  carbonate  in  80  parts  of  boiling  water. 
Add  this  solution  to  the  united  filtrates  obtained  from  the  chlorin- 
ated lime  mixtures.  Stir  the  mixture  thoroughly,  and,  if  it  should 
become  gelatinous,  apply  heat  until  liquefaction  is  effected.  Trans- 
fer the  mixture  to  a  new  filter,  collect  the  filtrate  and  add  as 
much  more  water,  through  the  filter,  as  may  be  necessary  to 
make  the  total  product  200  parts. 

Keep  the  solution  in  well-stoppered  bottles,  protected  from  light 
and  in  a  cool  place. 

Reaction. 

Ca(OCl)2+CaCl2+2Na2CO3=2NaOCl+2NaCl+2CaCO,. 

Notes.  The  object  of  using  hot  solution  of  sodium  carbonate 
is  to  produce  a  dense  calcium  carbonate,  which  settles  more 
readily  than  a  lighter  precipitate.  At  the  same  time  it  should  be 
remembered  that  high  heat  decomposes  the  hypochlorite  of  so- 


59O  SODIUM  HYPOCHLORITE. 

dium  formed,  and  the  value  of  the  preparation  would  then  be 
impaired  by  loss  of  available  chlorine.  On  the  addition  of  acids 
the  solution  effervesces  because  carbon  dioxide  and  chlorine  are 
liberated;  the  CO2  comes  from  the  excess  of  sodium  carbonate. 
The  containers  should  be  closed  with  rubber  stoppers  or  glass 
stoppers  instead  of  corks,  as  the  chlorine  destroys  the  latter. 

Description. — A  pale-greenish  clear  liquid,  having  a  faint  odor 
of  chlorine,  and  an  alkaline  as  well  as  salty  and  peculiar  taste. 
Sp.  w.  about  1.052.  Colors  red  litmus  paper  blue  and  then 
bleaches  it.  On  the  addition  of  hydrochloric  acid  the  liquid  gives 
off  chlorine  and  carbon  dioxide. 


SODIUM    HYPOPHOSPHITE. 

SODII    HYPOPHOSPHIS. 

NaPO2H2.H2O=io6. 

Calcium  hypophosphite 6  parts 

Sodium  carbonate 10  parts 

Dissolve  each  salt  in  60  parts  of  boiling  water,  and  mix  the 
solutions.  Filter  out  the  calcium  carbonate,  and  evaporate  the 
solution  over  a  water-bath  until  a  dry  granular  salt  remains, 
taking  care  that  the  temperature  during  the  evaporation  does  not 
exceed  85°  C. 

Notes.  May  be  purified  by  re-dissolving  it  in  ten  times  its 
weight  of  hot  alcohol,  filtering,  and  evaporating  to  dryness. 

Reaction.     Ca(H2PO2)2+Na2CO3=CaCO3+2NaH2PO2. 

Description. — Pearly  white  or  colorless  crystals,  or  a  white 
granular  powder ;  odorless  ;  taste  saline,  bitterish.  Hygroscopic. 
Soluble  at  15°  in  its  own  weight  of  water  and  in  30  parts  of 
alcohol;  in  0.12  part  of  boiling  water  and  in  its  own  weight  of 
boiling  alcohol.  Insoluble  in  ether.  The  water-solution  is  neu- 
tral to  litmus  paper. 


SODIUM    IODIDE.  59! 

SODIUM    IODIDE. 

SODII    IODIDUM. 

=  149.5. 

wire,  cut  .........................  6  parts 

Iodine  ...............................  20  parts 

Sodium  carbonate  .....................  24  parts 

Distilled  water,  sufficient. 

Digest  the  iron  and  15  parts  of  the  iodine  with  50  parts  of 
water  in  a  flask  until  the  odor  of  iodine  ceases  and  a  green  solu- 
tion of  ferrous  iodide  results.  Filter  this,  and  dissolve  the  re- 
mainder of  the  iodine  in  the  filtrate.  Dissolve  the  sodium  car- 
bonate in  80  parts  of  water,  heat  to  boiling,  then  add  the  solution 
of  iodides  of  iron  during  constant  stirring,  boil  the  mixture  fifteen 
minutes,  filter,  evaporate,  and  crystallize. 

Notes.  The  reactions  are  analogous  to  those  taking  place  in 
the  process  for  preparing  potassium  iodide  in  a  similar  way.  See 
the  notes  under  that  title. 

Sodium  iodide  may  also  be  made  from  iodine  and  solution  of 
sodium  hydroxide,  as  potassium  iodide  is  prepared  from  iodine 
and  solution  of  potassium  hydroxide. 

Description.  —  Colorless  crystals  or  a  white  crystalline  powder  ; 
odorless;  taste  saline,  somewhat  bitterish.  Hygroscopic.  De- 
composes when  exposed  to  the  air,  forming  sodium  carbonate  and 
free  iodine  which  discolors  the  product.  Soluble  at  15°  in  0.6 
part  of  water  and  in  about  3  parts  of  alcohol  ;  in  one-third  its 
weight  of  boiling  water  and  in  1.4  parts  of  boiling  alcohol.  The 
water-solution  should  be  neutral  or  only  faintly  alkaline  to  test- 
paper. 

SODIUM    NITRATE. 

SODII    NITRAS. 


Crude  sodium  nitrate  occurs  native  in  Peru  and  Bolivia.     The 
native  sodium  saltpeter  contains  from  20  to  80  per  cent  of  so- 


SODIUM    NITRATE. 

dium  nitrate,  most  frequently  yielding  50  per  cent.  It  is  freed 
from  earth  and  other  impurities  by  solution,  straining,  and  crys- 
tallization. 

It  is  purified  in  the  same  way  as  potassium  nitrate,  by  re- 
crystallization  and  by  washing  with  a  cold  saturated  solution  of 
pure  sodium  nitrate,  which  removes  chlorides  present. 

It  can  be  prepared  by  the  neutralization  of  diluted  nitric  acid 
with  sodium  carbonate. 

Description. — Colorless  transparent  crystals ;  odorless ;  taste 
saline,  cooling,  bitterish.  Hygroscopic.  Soluble  in  1.3  parts  of 
water  and  in  100  parts  of  alcohol  at  15°  ;  in  0.6  part  of  boiling 
water  and  in  40  parts  of  boiling  alcohol.  The  'ater-solution  is 
neutral  to  litmus  paper. 

SODIUM    NITRITE. 

SODII    NITRIS. 

NaNO2=69. 

Prepared  by  fusing  together  sodium  nitrate  and  sheet  lead, 
keeping  the  two  substances  together  at  the  temperature  required 
for  fusion  until  the  lead  oxidizes  to  lead  oxide  at  the  expense  of 
the  sodium  nitrate  which  is  thus  reduced  to  sodium  nitrite.  The 
nitrite  is  leached  out  from  the  cooled  mass  with  water  and  the 
solution  treated  with  carbon  dioxide  to  free  it  from  lead,  after 
which  the  liquid  is  filtered  and  evaporated  to  crystallization. 

Description. — Colorless  crystals  fused  into  white  masses  or 
sticks ;  odorless ;  taste  mild,  saline.  Hygroscopic.  Oxidizes  in 
air  to  nitrate.  Soluble  at  15°  in  1.5  parts  of  water.  Freely  sol- 
uble in  boiling  water.  Sparingly  soluble  in  alcohol.  The  water- 
solution  has  an  alkaline  reaction  on  test-paper. 

SODIUM    NITROPRUSSIDE. 

SODII    NITROPRUSSIDUM. 

Na2Fe  ( CN )  5NO.2H2O=3oo. 

Potassium  f errocyanide I  part 

Nitric  acid  (69%" HNO3) 2  parts 

Sodium  carbonate,  anhydrous,  about 2  parts 

Water. 

Reduce  the  ferrocyanide  to  fine  powder.     Dilute  the  nitric  acid 


SODIUM    NITROPRUSSIDE.  593 

with  about  i|  parts  of  water  in  a  flask.  Add  the  powder  in  small 
portions  to  the  acid,  shaking  after  each  addition,  and  waiting  until 
effervescence  ceases  before  adding  more.  When  all  of  the  fer- 
rocyanide  has  been  added  heat  the  mixture  at  full  water-bath  heat 
for  one  hour,  or  until  a  test  sample  of  the  liquid  no  longer  gives 
a  precipitate  on  addition  of  a  solution  of  ferric  chloride.  Then 
set  the  flask  aside  in  a  cool  place  for  about  twelve  hours.  De- 
cant the  green  liquid  from  the  crystals  of  potassium  nitrate. 
Neutralize  the  liquid  with  a  sufficient  quantity  of  sodium  car- 
bonate added  in  small  portions.  Heat  the  liquid  to  the  boiling 
point  to  expel  any  carbonic  acid,  and  then  add  a  concentrated 
solution  of  sodium  carbonate,  in  small  portions,  stirring  well, 
until  the  liquid  becomes  quite  neutral  again,  but  avoiding  an  ex- 
cess of  the  alkali  carbonate.  Filter  while  hot.  Evaporate  the 
filtrate  in  a  porcelain  dish  until  a  large  quantity  of  crystals  has 
separated.  Pour  off  the  hot  mother-liquor.  Collect  and  drain 
the  crystals,  and  then  dry  them  over  sulphuric  acid. 

Evaporate  the  mother-liquor  to  obtain  an  additional  crop  of 
crystals  out  of  the  hot  liquid  and  collect,  drain,  and  dry  them  as 
before,  avoiding  the  deposit  of  any  nitrate. 

Redissolve  the  crystals  in  twice  their  weight  of  hot  water,  filter 
into  an  evaporation  dish  and  set  this  over  sulphuric  acid  in  a 
desiccator,  in  a  shady  place.  Change  the  sulphuric  acid  as  often 
as  may  be  necessary. 

Notes.  Slow  evaporation  is  necessary  to  obtain  large  crystals. 
The  sulphuric  acid  should  be  changed  every  two  or  three  days. 
At  all  stages  of  the  process  the  product  must  be  protected  against 
strong  light. 

Properties.  Large,  fine,  blood-red  crystals,  soluble  in  2.5  parts 
of  water.  Decomposed  by  light  when  in  solution. 

SODIUM    OLEATE. 

SAPO    MEDICINALIS    DURUS. 
OLIVE    OIL    SOAP. 

["Medicinal  Soap."] 

Olive  oil 100  parts 

Sodium  hydroxide 15  parts 

Distilled   water 35  parts 

Alcohol    30  parts 

11-38 


594  SODA  SOAP. 

Dissolve  the  sodium  hydroxide  in  the  water,  add  the  oil  and 
the  alcohol,  and  heat  the  mixture  gently,  in  a  porcelain  dish,  over 
a  water-bath,  stirring  constantly,  until  saponification  is  com- 
pleted. Then  add  300  parts  of  warm  distilled  water  and  mix  well. 


Make  a  solution  of- — 


Sodium   chloride 25  parts 

Sodium    carbonate 5  parts 

Distilled   water 80  parts 


and  filter  it.     Add  this  solution  to  the  solution  of  the  soap,  and 
mix  thoroughly. 

Heat  the  mixture  over  the  water-bath,  stirring  gently,  until  the 
soap  separates  and  rises  to  the  surface  of  the  liquid.  Let  the  dish 
and  contents  cool.  When  cold  separate  the  mother  liquor  from 
the  soap,  and  rinse  the  soap  with  a  little  cold  water.  Then 
squeeze  the  water  out  of  the  soap  by  means  of  strong  pressure, 
dry  the  mass  with  the  aid  of  gentle  heat,  and  powder  the  product. 

Notes.  The  quantity  of  sodium  hydroxide  prescribed  is  slightly 
in  excess  of  the  amount  theoretically  required.  All  hard  soaps 
consist  mainly  of  sodium  oleate.  The  best  Castile  soap  ap- 
proaches pure  sodium  oleate  sufficiently  for  all  practical  purposes 
in  pharmacy,  including  the  preparation  of  other  oleates  by 
"double  decomposition."  No  soda  soap  should  be  used  for  the 
preparation  of  other  metallic  oleates  except  after  complete  drying ; 
hence  powdered  soap  is  to  be  used.  This  is  because  the  amount 
of  moisture  in  powdered  soap  can  not  vary  a  great  deal. 

The  soap  is  completely  soluble  in  water  although  the  solution  is 
not  clear.  Soda  soap  is  precipitated  from  its  water  solution  by 
sodium  chloride  in  the  manner  described. 

Transparent  soap  may  be  made  by  dissolving  soda  soap  in 
alcohol,  filtering  the  solution,  and  evaporating.  Castor  oil  soap 
easily  forms  a  transparent  soap. 

Medicinal  soda  soaps  are  sometimes  made  from  almond  oil,  and 
also  from  fresh  (unsalted)  butter. 


SODIUM  PHENOLSULPHONATE.  595 

SODIUM    PHENOLSULPHONATE. 

SODII    PARAPHENOLSULPHONAS. 

(Sodium  Sulphocarbolate.) 
NaC6H5S04.2H20=232. 

Crystallized  phenol 10  parts 

Sulphuric  acid 12  parts 

Barium   carbonate 20  parts 

Sodium    carbonate 34  parts 

Add  the  phenol  to  the  sulphuric  acid,  stir,  and  heat  the  mix- 
ture at  55°  C.  for  several  days.  Add  200  parts  of  water,  and  stir 
well.  Then  gradually  add  the  barium  carbonate,  and  mix  the 
whole  intimately.  Filter.  Precipitate  the  filtrate  exactly  with 
the  sodium  carbonate,  previously  dissolved  in  100  parts  of  water. 
Again  filter,  and  evaporate  to  crystallization.  Purify  the  product 
by  re-crystallization  until  colorless,  or  but  faintly  pinkish. 

Reaction. 

2HC6H5SO4+BaCO3=Ba(C6H5SO4)2+H2O+CO2;  and  then 
Ba(C6H5S04)2+Na2C03=2NaC6H5S04+BaC03. 

Notes.  Any  excess  of  sulphuric  acid  present  in  the  phenol-sul- 
phonic  acid  is  removed  by  the  use  of  an  excess  of  barium  car- 
bonate, whereby  insoluble  barium  sulphate  is  formed,  which  is 
filtered  away. 

Description. — Colorless,  transparent,  rhombic  prisms,  perma- 
nent in  the  air,  odorless  or  nearly  so,  having  a  cooling,  saline, 
somewhat  bitter  taste,  and  a  neutral  reaction.  Soluble  in  5  parts 
of  water,  and  in  132  parts  of  alcohol  at  15°  C.  (59°  F.)  ;  in  0.7 
part  of  boiling  water  and  in  10  parts  of  boiling  alcohol. 

SODIUM    PHOSPHATE. 

SODII      PHOSPHAS. 

Na2HP04.i2H20=358. 
[Di-Sodium-Hydrogen  Phosphate.] 

Bone-ash,  in  fine  powder 10  parts 

Sulphuric  acid   6  parts 

Sodium  carbonate,  sufficient. 


596  SODIUM  PHOSPHATE. 

Wash  the  bone-ash  with  ten  times  its  weight  of  boiling  water. 
Decant  and  reject  the  water.  Mix  the  wet  mass  with  the  acid, 
set  the  mixture  in  a  warm  place  for  three  days,  replacing  the 
water  vaporized  by  the  heat,  and  stir  occasionally.  Then  add  10 
parts  of  boiling  water,  mix  thoroughly,  transfer  the  mixture  to  a 
muslin  strainer,  and  let  the  liquid  pass  through.  Reserve  the 
liquid.  Transfer  the  magma  from  the  muslin  to  an  earthenware 
vessel,  add  10  parts  of  boiling  water,  stir  well,  and  again  strain 
the  mixture  through  muslin,  adding  the  colature  to  that  previously 
reserved.  Continue  washing  the  residue  with  boiling  water  until 
the  liquid  passes  nearly  tasteless.  Mix  the  several  acid  liquids 
and  evaporate  the  mixture  to  20  parts.  Set  this  aside  a  few  days. 
Filter.  Heat  the  filtrate  to  the  boiling  point,  and  gradually  add  to 
it  a  solution  of  sodium  carbonate  in  hot  water,  until  a  filtered  por- 
tion of  the  now  alkaline  liquid  effervesces  when  mixed  with  dilute 
sulphuric  acid.  Digest  the  mixture  an  hour  or  two,  and  then 
filter.  Wash  out  the  remaining  sodium  phosphate  from  the  resi- 
due by  means  of  hot  water,  adding  the  washings  to  the  filtrate. 
Then  evaporate  the  mixed  liquids  to  10  parts,  and  set  aside  to 
crystallize. 

Purify  the  product  by  re-crystallization  after  dissolving  it  in 
twice  its  weight  of  water.  Repeat  the  re-crystallization  as  many 
times  as  may  be  necessary  to  obtain  a  clean  product. 

Dry  the  crystals  with  as  little  exposure  to  the  air  as  possible, 
to  avoid  efflorescence. 

Reaction.  First  the  tri-calcium  phosphate  (bone-ash)  is  de- 
composed by  the  sulphuric  acid  yielding  acid  calcium  phosphate 
and  calcium  sulphate  as  follows : 

Ca3  ( PO4)  2+2H2SO4=CaH4  ( PO4 )  2+2CaSO4. 

Then  the  acid  phosphate  of  calcium  is  decomposed  by  the  so- 
dium carbonate  as  follows: 

CaH4(P04)2+2Na2C03=2Na2HP04+CaC03+C02+H20. 

Notes.  When  the  bone-ash  is  treated  with  sulphuric  acid  the 
mixture  becomes  hot.  Usually  the  powdered  bone-ash  is  not 
washed  previous  to  mixing  it  with  the  sulphuric  acid,  and  no 
water  added  until  after  the  powder  and  acid  have  first  been  thor- 
oughly mixed.  If  organic  matter  be  present  in  the  bone-ash,  sul- 


SODIUM  PHOSPHATE.  597 

phur  dioxide  is  given  off.  Some  carbon  dioxide  will  also  be  given 
off  from  calcium  carbonate  in  the  bone-ash.  If  the  bone-ash  is 
washed  with  water,  the  object  of  which  is  the  removal  of  alkalies, 
the  wash-water  should  be  drained  off  thoroughly  before  mixing 
the  moist  mass  with  the  acid.  When  the  process  is  carried  out 
on  a  small  scale  the  washed  and  drained  bone-ash,  still  wet, 
should  be  put  in  a  tared  vessel,  the  sulphuric  acid  mixed  with  it, 
and  finally  enough  boiling  water  added  to  make  the  whole  mixture 
weigh  three  times  as  much  as  the  bone-ash  used.  After  the  mass 
has  been  digested  a  sufficient  time  to  insure  thorough  decom- 
position of  the  basic  calcium  phosphate,  to  facilitate  which  the 
mass  should  be  frequently  and  thoroughly  stirred,  the  next  step 
is  the  separation  of  the  liquid  containing  the  acid  phosphate  of  cal- 
cium, with  which  the  sodium  phosphate  is  to  be  made,  from  the 
white  mass  of  calcium  sulphate  which  is  to  be  thrown  away  after 
the  acid  liquid  has  been  completely  washed  out  from  it  and  col- 
lected. 

On  a  manufacturing  scale  this  leaching  process  may  be  con- 
veniently carried  out  in  tubs  provided  with  loose  perforated  dia- 
phragms resting  on  suitable  supports  about  four  or  five  inches 
above  their  bottoms.  A  common  tight  barrel  sawed  in  two  in 
the  middle  furnishes  two  good  tubs.  A  hole  is  bored  in  one  side 
of  each  tub,  about  two  inches  above  the  bottom,  and  a  tube  about 
six  inches  in  length  is  fitted  tightly  in  the  hole.  A  piece  of  very 
coarse,  loose  gunny-bagging  is  washed  in  warm  water  and,  while 
still  wet,  spread  out  over  the  perforated  false  bottom  so  as  to  cover 
it  and  extend  two  or  three  inches  up  on  the  sides  of  the  tub  all 
around.  The  mixture  of  bone-ash,  acid  and  water  is  now  put  into 
the  tub,  which  should  be  about  half  filled.  A  stick  of  wood  four 
feet  long  furnishes  a  good  stirrer.  Boiling  water  is  now  poured 
upon  the  mass  and  well  mixed  with  it,  after  which  the  liquid  is 
allowed  to  percolate  through  the  mass,  and  through  the  strainer, 
into  the  space  between  the  perforated  diaphragm  and  the  bottom 
of  the  tub,  and  to  run  out  through  the  tube  into  a  bucket,  or  other 
suitable  vessel. 

When  the  liquor  which  passes  from  the  tub  is  nearly  tasteless, 
or  no  longer  acid,  the  leaching  is  completed,  the  residue  of  calcium 
sulphate  is  thrown  away,  and  the  acid  liquor  is  boiled  down  to 
twice  the  weight  of  the  bone-ash  used. 

The  concentrated  solution  of  acid  calcium  phosphate  is  now 


59^  SODIUM  PHOSPHATE. 

allowed  to  stand  a  few  days  in  order  that  the  calcium  sulphate  held 
in  solution  may  be  deposited.  It  is  then  filtered,  diluted  with  an 
equal  volume  of  water,  and  heated  to  the  boiling  point.  To  the 
hot  liquid  is  now  added  hot  sodium  carbonate  solution  as  de- 
scribed. 

The  quantity  of  sodium  carbonate  required  will  depend  upon 
the  completeness  of  the  decomposition  of  the  bone-ash  and  the 
lixiviation — in  other  words,  upon  the  amount  of  acid  calcium 
phosphate  contained  in  the  liquor.  If  the  work  has  been  well 
done,  it  will  require  about  100  parts  or  more  of  sodium  carbonate 
to  render  alkaline  the  acid  liquor  from  100  parts  of  bone-ash. 

Hot  liquids  are  employed  in  order  that  the  calcium  carbonate 
formed  may  be  heavy,  so  as  to  separate  as  rapidly  as  possible. 
The  sodium  carbonate  must  be  added  gradually,  because  of  the 
effervescence  caused  by  the  escaping  carbonic  oxide.  Litmus 
paper  cannot  be  used  to  ascertain  when  sufficient  sodium  car- 
bonate has  been  added,  because  sodium  phosphate  itself  has  an 
alkaline  reaction.  After  the  further  addition  of  sodium  carbonate 
has  ceased  to  cause  effervescence,  it  is  necessary  to  remove  a  small 
portion  of  the  liquid,  filter  it,  and  test  it  by  pouring  it  into  a  small 
amount  of  dilute  sulphuric  acid,  when  it  should  effervesce.  The 
slight  excess  of  sodium  carbonate  added  is  necessary  to  insure 
satisfactory  crystallization  of  the  sodium  phosphate,  and  the  car- 
bonate remains  in  the  mother-liquor. 

When  the  liquid  contains  an  excess  of  sodium  carbonate,  the 
precipitated  calcium  carbonate  is  filtered  out  and  washed  on  the 
filter  with  a  little  hot  water,  the  washings  being  added  to  the 
previous  filtrate.  Evaporate  the  filtrate  until  reduced  to  about 
three  times  the  weight  of  the  sodium  carbonate  consumed,  or 
until  a  pellicle  begins  to  form  on  the  surface.  Then  set  it  aside  to 
crystallize. 

The  crystallization  is  best  effected  when  an  excess  of  sodium 
carbonate  is  present  and  the  solution  is  not  too  concentrated.  It 
should  not  be  hastened  by  evaporating  down  the  solution  too  far, 
because  the  salt  then  crystallizes  with  only  7  instead  of  12  mole- 
cules of  water  of  crystallization. 

The  product  generally  requires  purification  by  recrystallization 
to  obtain  a  sodium  phosphate  which  answers  the  description  and 
tests  of  the  Pharmacopoeia. 

Description. — Colorless  transparent  crystals,  having  a  specific 


SODIUM  PHOSPHATE.  599 

gravity  of  1.55.  They  effloresce  readily,  and  when  slightly  heated 
melt  in  their  water  of  crystallization. 

The  salt  is  odorless,  and  has  a  cooling,  saline,  somewhat  alka- 
line, taste.  Efflorescent. 

Soluble  in  5.8  parts  of  water  at  15°,  and  in  1.5  parts  of  boiling 
water.  Insoluble  in  alcohol.  The  water-solution  is  alkaline  to 
litmus  paper,  but  not  to  phenolphtalein  paper. 

Recrystallized  Sodium  Phosphate. 

Sodium  carbonate I  part 

Commercial  sodium  phosphate 50  parts 

Water    250  parts 

Dissolve  the  sodium  phosphate  in  the  water  with  the  aid  of 
heat,  filter  the  solution,  put  it  in  a  crystallizer  and  set  this  aside 
at  perfect  rest  in  a  place  free  from  dust  that  crystals  may  form  by 
spontaneous  evaporation  of  the  solvent  at  the  ordinary  room 
temperature. 

Should  crystallization  be  much  delayed  place  a  few  clear  crys- 
tals of  pure  sodium  phosphate  in  the  solution  to  start  it. 

Collect  the  crystals  in  the  usual  way,  drain  them,  press  them 
gently  between  cloths  or  bibulous  paper,  dry  them  hastily,  and 
at  once  put  the  product  in  dry  bottles,  which  must  be  tightly 
closed  and  kept  in  a  cool  place. 

Dried  Sodium  Phosphate. 
Na2HPO4=i42. 

Heat  crystallized  sodium  phosphate  in  porcelain  dish  over  a 
water-bath  until  it  ceases  to  lose  weight,  stirring  the  contents  until 
dry.  Then  heat  the  powder  on  a  sand-bath  at  about  120°  C.  for 
a  few  minutes.  Keep  the  product  in  a  tightly-closed  bottle. 

Notes.  Crystallized  sodium  phosphate  contains  12  molecules 
of  water  of  crystallization.  When  heated  to  35°  C.  it  begins  to 
liquefy,  but  does  not  completely  dissolve  until  at  about  40°  C. 
If  then  allowed  to  cool  at  once  it  solidifies  to  a  cake  of  a  radiated 
crystalline  texture. 

When  heated  above  40°  C.  the  salt  loses  5  molecules  of  water. 

At  100°  C.  all  the  water  of  crystallization  is  finally  expelled 
and  "dried  sodium  phosphate"  remains.  But  as  water-bath  heat 


600  SODIUM  PHOSPHATE. 

is  not  sufficient  (being  less  than  100°  C.)  to  effect  this  result.,  the 
drying  must  be  finished  with  the  aid  of  the  sand-bath. 

"Effloresced  sodium  phosphate,"  formed  by  the  gradual  drying 
of  the  crystallized  salt  in  dry  warm  air,  contains  47  per  cent  of 
water,  or  seven  molecules,  and  the  "dried  sodium  phosphate"  (an- 
hydrous) gradually  absorbs  moisture,  when  exposed  to  the  air, 
until  converted  into  Na2HPO4.7H2O. 

Description. — A  white,  amorphous  powder. 

Sodium  Ammonium  Phosphate. 

SODII  ET  AMMONII  PHOSPHAS. 

[Microcosmic  Salt.] 
NH4NaHPO4.4H2O=4i8. 

Sodium  phosphate 5  parts 

Ammonium  phosphate   2  parts 

Dissolve  the  salts  in  20  parts  of  hot  water,  add  a  little  ammonia 
so  as  to  render  the  liquid  alkaline  to  turmeric  paper,  filter,  and 
set -aside  to  crystallize. 

The  crystals  effloresce;  their  solution  has  a  slightly  alkaline 
reaction. 

The  salt  is  used  as  a  reagent  in  blow-pipe  analysis. 

SODIUM    PYROPHOSPHATE. 

SODII    PYROPHOSPHAS. 

Na4P2O7.ioH2O=446. 

Prepared  by  heating  sodium  phosphate  in  an  iron  dish,  raising 
the  heat  gradually  until  the  salt  fuses  in  its  water  of  crystalliza- 
tion, then  falls  to  powder  as  that  water  is  expelled,  and  finally 
decomposes  at  a  temperature  of  240°  to  300°  C.,  being  converted 
into  normal  sodium  pyrophosphate.  The  dry  powder  is  dissolved 
in  a  sufficient  quantity  of  boiling  water — about  five  times  its 
weight — the  solution  is  filtered  while  hot,  and  then  set  aside  to 
crystallize.  More  crystals  are  to  be  obtained  from  the  mother 
liquor  upon  evaporation. 

Reaction.    2Na2HPO4=Na4P:JO7+H2O. 


SODIUM    PYROPHOSPHATE.  6oi 

Notes.  Sodium  phosphate,  in  solution,  yields  a  yellow  precipi- 
tate with  test-solution  of  silver  nitrate  acidulated  with  nitric  acid ; 
sodium  pyrophosphate  yields  a  perfectly  white  precipitate  with 
the  same  reagent.  The  conversion  of  the  phosphate  is,  therefore, 
kno\vn  to  be  completed  when  a  sample  of  the  dry  powder,  dis- 
solved in  water,  yields  a  white  precipitate  with  silver  nitrate. 

From  716  parts  of  sodium  phosphate,  the  yield  of  pyrophosphate 
of  sodium  should  be  446  parts,  or  nearly  62  per  cent. 

Description. — Colorless,  transparent  crystals,  odorless,  of  cool- 
ing, saline,  somewhat  alkaline,  taste.  Soluble  in  12  parts  of  water 
at  15°  and  in  i.i  parts  of  boiling  water.  Insoluble  in  alcohol.  The 
water-solution  has  a  slightly  alkaline  reaction  on  both  litmus  paper 
and  phenolphtalein. 

SODIUM   SALICYLATE. 

SODII     SALICYLAS. 

NaC7H5O2=i6o. 

Salicylic  acid    10  parts 

Sodium  bicarbonate    6  parts 

Water 40  parts 

Shake  the  salicylic  acid  well  with  the  water  so  as  to  distribute 
it  uniformly  through  the  liquid.  Then  add  the  sodium  bicarbonate, 
a  little  at  a  time,  shaking  well  after  each  addition.  Warm  the 
liquid  slightly  to  expel  the  carbonic  acid  which  is  set  free.  When 
cold  again,  filter  the  solution,  and  evaporate  at  not  over  60°  C. 
to  dryness,  stirring  constantly  so  as  to  obtain  a  granulated  product. 
Keep  it  in  well  stoppered  bottles  in  a  cool  place  and  protected 
against  light. 

Reaction.    2HC7Hr,O3-f2NaHCO3 
=2NaC7H5O3+2H2O-f-2CO2. 

Notes.  It  is  important  that  salicylic  acid  should  be  in  excess 
throughout ;  consequently  a  small  excess  of  the  acid  is  used,  and 
the  sodium  bicarbonate  added  to  the  acid  instead  of  vice  versa. 
Should  the  alkali  be  in  excess,  the  product  may  become  darkened 
even  during  the  process  of  manufacture,  and  never  fails  to  be 


CO2  SODIUM     SALICYLATE. 

dark-colored   when  finished  or  after  being  kept  a  short  time. 

E.  Hoffman  recommends  preparing  the  salt  by  stirring  20  parts 
of  sodium  bicarbonate  and  33  parts  of  dialyzed  salicylic  acid  with 
enough  water  to  form  a  thick  paste,  allowing  the  carbonic  acid 
time  to  escape,  and  then  evaporating  to  dryness. 

The  presence  of  iron  (even  mere  traces)  causes  a  reddish  dis- 
coloration of  the  salt  and  solutions  of  it.  Hence  filter  paper  quite 
free  from  iron  must  be  used. 

A  crystallized  product  may  be  obtained  from  a  saturated  alco- 
holic solution.  The  crystals  should  then  be  drained  in  a  funnel 
and  dried  in  a  porcelain  dish  with  the  aid  of  moderate  heat.  An 
additional  quantity  of  salt  may  be  recovered  from  the  mother- 
liquor  on  evaporation.  Should  the  mother-liquor  be  colored  it 
may  be  decolorized  by  filtration  through  animal  charcoal  unless 
the  coloration  is  due  to  iron.  The  salicylic  acid  contained  in  the 
last  mother-liquor  can  be  recovered  by  evaporating  to  dryness, 
redissolving  the  residue  in  water  and  precipitating  by  adding  an 
excess  of  diluted  sulphuric  acid. 

Description. — A  white,  amorphous  or  crystalline  powder,  odor- 
less, sweetish,  saline,  afterwards  acrid.  Soluble  in  0.9  part  of 
water,  and  in  6  parts  of  alcohol  at  15°.  Very  soluble  in  these  sol- 
vents at  their  boiling  points.  Soluble  also  in  glycerin.  The  water- 
solution  should  have  a  slightly  acid  reaction  on  test-paper. 


SODIUM    SANTONINATE. 

SODII    SANTONINAS. 

2NaC15H1904.7H20= 698. 

Santonin 10  Gm 

Solution  of  soda 35  Gm 

Water    10  Gm 

Mix  and  digest  until  dissolved;  filter,  set  in  a  cool  place  to 
crystallize.  Evaporate  the  mother-liquor  to  recover  more,  as  long 
as  the  crystals  obtained  are  colorless. 

Keep  it  in  a  tightly-corked  bottle,  and  protected  from  the  light. 

Recover  the  remainder  of  the  santonin  from  the  last  mother- 


SODIUM      SAN  TON  IN  ATE.  603 

liquor  by  acidulating  with  hydrochloric  acid,  when  it  will  sep- 
arate in  crystalline  form. 

Albuminated  Santoninate  of  Sodium. 

Santonin    10  Gm 

Sodium  bicarbonate 40  Gm 

Dry  soluble  albumen 20  Gm 

Water    . .  500  ml 

Digest  together  at  60°  C.  until  dissolved.     Filter.     Evaporate 
by  gentle  heat.    Spread  it  on  glass  plates  to  dry. 
Brilliant  pearly  scales,  soluble  in  water. 


SODIUM    SILICATE    SOLUTION. 

LIQUOR    SODII    SILICATIS. 

(Water-glass.    Soluble  glass.    Liquid  glass.) 

Containing  33  per  cent  of  a  mixture  of  sodium  tri-silicate 
(Na2Si3O7)  and  sodium  tetrasilicate  (Na2Si4O9).  It  must  be  free 
from  caustic  alkali. 

When  an  intimate  mixture  of  one  molecule  of  dried  sodium 
carbonate  and  four  molecules  of  silica  are  fused  together,  the 
fused  mass  is  water-soluble,  and  a  solution  having  a  sp.  w.  of  from 
1.30  to  1.40  is  employed  for  surgical  dressings.  It  is  a  syrupy, 
colorless,  odorless  liquid. 

SODIUM    SULPHATE. 

SODII    SULPHAS. 

Na2SO4.ioH2O=322. 
[Glauber's  Salt.] 

Obtained  as  a  bye-product  in  the  manufacture  of  hydrochloric 
acid  from  sodium  chloride  and  sulphuric  acid.  Also  in  many 
other  chemical  processes. 

The  crude  Glauber's  Salt  may  be  purified  as  follows : 


604  SODIUM     SULPHATE. 

Crystallised  Sodium  Sulphate. 

Glauber's  salt 2  parts 

Water    3  parts 

Lime, 
Chlorinated  lime. 

Dissolve  the  salt  in  the  water  and  the  solution  to  the  boiling 
point. 

Slake  a  piece  of  lime,  and  add  water  enough  to  form  a  thick, 
milky  mixture;  of  this  "milk  of  lime"  add  so  much  to  the  hot 
solution  of  Glauber's  salt  to  render  it  alkaline  to  test  paper.  Stir 
well. 

Mix  some  chlorinated  lime  with  enough  water  to  form  a  thick, 
milky  mixture ;  of  this  add  a  small  quantity  at  a  time  to  the  solu- 
tion of  Glauber's  salt  until  a  filtered  test  sample  no  longer  becomes 
discolored  by  hydrogen  sulphide  after  acidulation  with  hydro- 
chloric acid. 

When  free  from  iron,  filter  the  liquid,  and  evaporate  the  filtrate 
until  it  has  acquired  the  sp.  w.  1.25  at  40°  C.  Set  the  solution 
aside  in  a  crystallizer,  at  rest,  and  let  crystallization  be  effected  in 
the  usual  way.  Drain  the  crystals,  press  them  gently  between 
cloths  or  bibulous  paper  until  dry,  and  at  once  place  them  in  dry 
bottles,,  which  are  to  be  tightly  closed. 

Pure  Sodium  Sulphate  may  also  be  made  from  diluted  sul- 
phuric acid  and  sodium  carbonate. 

Description. — Large,  colorless,  transparent  crystals,  odorless ;  of 
somewhat  bitter,  saline  taste.  Efflorescent  in  air.  Soluble  at  15° 
in  2.8  parts  of  water ;  at  34°  in  one- fourth  its  weight  of  water ; 
at  100°  in  0.47  part  of  water.  Insoluble  in  alcohol.  Neutral. 

Carlsbad  Salt. 

Dried  sodium  sulphate 22  parts 

Sodium  bicarbonate 18  parts 

Sodium  chloride    9  parts 

Potassium  sulphate I  part 

• 

Mix  the  previously  powdered  dry  salts. 

[Carlsbad  water  contains  about  6  Gm  of  salts  to  each  liter.] 


SODIUM     SULPHATE.  605 

Notes.  The  chloride  and  the  bicarbonate  must  be  well  dried, 
separately,  and  then  powdered.  The  sulphate,  in  crystals,  should 
also  be  powdered  separately,  which  can  hardly  be  effected  other- 
wise than  by  granulating  the  previously  dissolved  salt.  If  dried 
sodium  sulphate  is  used,  the  product  will  yield  hard  lumps  when 
water  is  added,  and  these  hard  particles  dissolve  but  slowly. 

Effervescent  Carlsbad  Salt. 

Artificial  Carlsbad  salt  ...............  100  parts 

Sodium  bicarbonate  ..................  100  parts 

Tartaric  acid    .......................     54  parts  ' 

Citric  acid  ..........................     36  parts 

Mix  the  powdered  ingredients  in  a  mortar,  transfer  the  mixture 
to  a  porcelain  dish  and  heat  it  over  a  water-bath,  stirring  con- 
stantly, until  a  pasty  mass  is  formed.  Granulate  this  by  passing 
it  through  a  very  coarse  sieve,  in  the  usual  way,  and  dry  the  prod- 
uct at  about  25°  C. 

Dried  Sodium   Sulphate. 
Na2SO4=i42. 

Place  the  crystallized  sodium  sulphate  in  a  porcelain  dish  over 
the  water-bath  and  expose  it  to  a  moderate  heat  until  reduced  to 
scarcely  more  than  44  per  cent  of  its  original  weight  and  com- 
pletely effloresced. 

Notes.  Crystallized  sodium  sulphate  contains  about  56  per 
cent  of  water  of  crystallization.  It  readily  parts  with  all  of  that 
water  even  at  ordinary  room  temperatures,  and  effloresces  very 
rapidly  when  moderately  heated. 

Description.  —  A  white,  amorphous  powder. 
SODIUM    SULPHITE. 

SODII     SULPHIS. 


Prepared  by  saturating  a  solution  of  sodium  carbonate  with  sul- 
phur dioxide,  and  then  adding  another  equal  quantity  of  sodium 
carbonate,  after  which  the  solution  is  evaporated  to  crystallization. 
The  process  is  analogous  to  that  for  making  potassium  sulphite. 


606  SODIUM     SULPHITE. 

In  both  cases  a  bisulphite  is  first  made,  and  this  is  converted  into 
normal  sulphite  by  the  addition  of  a  quantity  of  the  alkali  equal 
to  the  amount  used  in  making  the  bisulphite. 

The  salt  must  be  kept  in  tightly-closed  bottles  in  a  cool  place. 

Description.  —  Colorless  prisms  or  powder,  resembling  potassium 
sulphite  in  most  of  its  properties.  Odorless. 

It  has  a  cooling,  saline,  sulphurous  taste.  Soluble  in  4  parts 
of  water  at  15°  ;  and  in  0.9  part  of  boiling  water.  Sparingly  sol- 
uble in  alcohol. 

SODIUM  TARTRATE. 

SODII     TARTRAS. 


Tartaric  acid   .......................   130  parts 

Sodium  carbonate  ...................  251  parts 

Distilled  water. 

Dissolve  the  sodium  carbonate  in  the  water.  Add  the  tartaric 
acid  gradually,  stirring  after  each  addition  until  dissolved.  Filter, 
evaporate  and  crystallize,  or  evaporate  the  filtrate  to  dryness  to 
obtain  a  granular  product. 

Eeaction.    Na2CO3+H2C4H4O6=Na2C4H4O6+H2O+CO2, 

Notes.  148  parts  of  sodium  bicarbonate  may  be  used  instead  of 
251  parts  of  normal  sodium  carbonate. 

Description.  —  Colorless,  transparent  crystals  ;  odorless  ;  of  cool- 
ing, mildly  saline  taste.  Soluble  in  5  parts  of  water  at  15°.  In- 
soluble in  alcohol.  Neutral  to  litmus  paper. 


SODIUM   TETRABORATE. 

SODII    TETRABORAS. 

Borax. 

Na2B4O7.ioH2O—  381. 
[Sodium  Borate.    Sodium  Pyroborate.] 

Borax  occurs  native  in  Persia,  Thibet,  and  other  western  Asiatic 
countries,  and  in  large  deposits  in  California  and  Nevada,  either 
alone  or  with  other  borates.  Most  of  the  borax  now  used  is  made 


BORAX.  607 

from  crude  boric  acid  by  fusion  with  dried  sodium  carbonate, 
solution  in  water,  and  crystallization. 

Description. — Colorless,  transparent  crystals  or  white  powder, 
inodorous,  having  a  sweetish,  alkaline  taste.  Slightly  efflorescent 
in  warm,  dry  air.  Soluble  in  16  parts  of  water  at  15°  C.  and  in 
one-half  its  own  weight  of  boiling  water.  Insoluble  in  alcohol. 
Soluble  in  I  part  of  glycerin  at  80°  C. 

Crystallised  Sodium  Tetraborate. 

Borax    I  part 

Water 16  parts 

Dissolve  the  borax  in  the  water  by  the  aid  of  heat,  filter  the 
solution,  and  crystallize  the  salt  by  spontaneous  evaporation  of  the 
solvent  in  the  usual  way. 

Turbidated   Bor-ax. 

Borax    I  part 

Boiling  water 2  parts 

Dissolve,  filter,  and  cool  the  solution  rapidly,  constantly  stirring 
it,  to  as  low  a  temperature,  above  freezing,  as  may  be  conveniently 
attained. 

Collect,  drain,  and  dry  the  salt. 


SODIUM    THIOSULPHATE. 

SODII     THIOSULPHAS. 


["Sodium  Hyposulphite."] 

This  salt,  which  is  a  monothiosulphate,  may  be  prepared  by  boil- 
ing sulphur  with  a  solution  of  sodium  hydroxide  and  then  passing 
sulphur  dioxide  into  the  liquid  until  colorless.  The  solution  is 
then  brought  to  crystallization. 

It  may  also  be  made  by  boiling  sulphur  with  a  solution  of  so- 
dium sulphite. 

Commercial  sodium  thiosulphate  may  be  purified  by  recrystal- 
lization.  For  this  purpose  it  should  be  dissolved  in  its  own  weight 


608  SODIUM     THIOSULPHATE. 

of  distilled  water,  the  solution  filtered,  and  evaporated  slowly. 
Large  crystals  are  easily  obtained. 

It  should  be  kept  in  tightly  closed  bottles. 

Description.  —  Colorless,  odorless  crystals,  soluble  in  0.65  part 
of  water  at  15°  C.  and  in  about  0.5  part  at  20°  C.  Insoluble  in 
alcohol. 

["Sodium  hyposulphite"  is  an  unfortunate  misnomer  for  real 
sodium  hyposulphite  is  Na2SO2.] 

SODIUM  VALERATE. 

SODII  VALERIAN  AS. 


Iso-amylic  alcohol  ....................  I  part 

Potassium  dichromate    ................  3  parts 

Sulphuric  acid   .......................  4  parts 

Water    ..............................  4  parts 

Solution  of  sodium  hydroxide,  sufficient. 

Dilute  the  sulphuric  acid  with  one-half  of  the  water.  Dissolve 
the  potassium  dichromate  in  the  remainder  of  the  water  with  the 
aid  of  heat.  When  both  liquids  are  cold  mix  them  with  the  amylic 
alcohol  in  a  retort  or  flask,  with  occasional  brisk  agitation  until 
the  temperature  of  the  mixture  has  fallen  to  about  32°  C.  Con- 
nect with  a  condenser,  and  distil  until  about  4  parts  of  distillate 
has  been  obtained.  Saturate  the  distilled  liquid  accurately  with 
the  solution  of  sodium  hydroxide,  remove  any  oily  fluid  which 
floats  on  the  surface,  evaporate  until  watery  vapor  ceases  to 
escape,  and  then  raise  the  heat  cautiously  until  the  salt  is  liquefied. 
When  the  product  has  cooled  and  solidified,  break  it  into  pieces, 
and  immediately  put  it  into  a  stoppered  bottle. 

Reaction.     3C5H12O+2K2Cr2O7+8H2SO4= 

3C5H1002+2K2S04+2  (  Cr2  (  SO4)  ,)  +  1  1  H2O. 

Notes.  The  dichromate  of  potassium  is  decomposed  by  the  sul- 
phuric acid,  the  products  being  potassium  sulphate  and  chromic 
acid.  The  amylic  alcohol  is  then  oxidized  by  the  chromic  acid, 
and  when  the  mixture  is  subjected  to  distillation,  the  distillate 
consists  of  valeric  acid  and  amyl  valerate  (or  apple  oil). 


SODIUM     VALERATE.  609 

When  sodium  hydrate  is  added  to  the  liquid,  the  amyl  valerate 
separates  as  an  oily  layer,  whilst  the  valeric  acid  is  neutralized, 
forming  sodium  valerate.  If  the  oily  amyl  valerate  be  warmed 
with  the  soda  solution  it  is  decomposed,  yielding  sodium  valerate 
and  amylic  alcohol,  which  also  appears  as  an  oily  liquid  on  the  sur- 
face of  the  solution.  After  removing  the  oily  fluid,  the  solution 
of  sodium  valerate  is  evaporated  and  the  salt  fused. 

Description.  —  White  crystals,  soluble  in  water  and  alcohol.  The 
crystals  absorb  water  from  moist  air,  and  liquefy.  They  melt 
without  decomposition,  at  a  temperature  of  140°. 

STRONTIUM   BROMIDE. 

STRONTII     BROMIDUM. 

SrBr2.6H20=355.5. 

Prepared  by  saturating  hydrobromic  acid  with  pure  strontium 
carbonate,  filtering,  and  evaporating  the  solution  to  crystalliza- 
tion. Instead  of  strontium  carbonate  the  hydroxide  may  be  used. 
(See  Strontium  hydroxide,  p.  6  IT.)  The  crystals  must  be  dried 
cautiously,  as  the  salt  effloresces  at  a  higher  temperature. 

Reaction.     SrCOs+2HBr=SrBr2+H2O+CO2. 

Strontium  bromide  may  also  be  prepared  from  the  hydroxide  by 
double  decomposition  with  either  ammonium  brc  nicle  or  iron 
bromide. 

Description.  —  Colorless,  transparent  crystals  ;  odorless  ;  taste 
saline,  bitterish.  Soluble  in  its  own  weight  of  cold  water,  and  in 
one-half  its  weight  of  boiling  water.  Readily  soluble  also  in 
alcohol. 

STRONTIUM    CARBONATE. 

STRONTII     CARBONAS. 


Dissolve  any  desired  quantity  of  commercial  strontium  nitrate 
in  ten  times  its  own  weight  of  distilled  water.  Add  gradually  and 
during  constant  stirring  a  water-solution  of  potassium  dichromate 
to  precipitate  any  barium  present  and  until  a  clear  yellow  liquid  is 
produced.  Let  the  liquid  stand  for  24  hours  ;  then  filter.  Add  to 

11-39 


6lO  STRONTIUM     CARBONATE. 

the  filtrate,  heated  at  a  temperature  of  100°  C.,  a  sufficient  quan- 
tity of  sulphurous  acid  to  cause  the  disappearance  of  the  char- 
acteristic color  of  the  chromic  acid  and  the  appearance  of  a  greenish 
color  due  to  the  formation  of  chromic  salt,  meanwhile  main- 
taining the  temperature  at  the  boiling  point  of  water.  Boil  the 
liquid  until  the  excess  of  sulphurous  acid  is  expelled.  Continue 
the  boiling  and  add  enough  strontium  carbonate  to  cause  the  com- 
plete precipitation  of  the  chronium  by  the  strontium  carbonate. 
Filter.  Pour  the  filtrate  into  a  filtered  solution  of  sodium  car- 
bonate used  in  excess.  Wash  the  precipitate  until  the  washings 
are  tasteless  and  leave  no  perceptible  residue  on  evaporation.  Dry 
the  product  at  a  moderate  heat. 

Description. — An  amorphous,  white,  odorless  and  tasteless,  in- 
soluble powder. 

STRONTIUM  CHLORIDE. 

STRONTII     CHLORIDUM. 

SrCl2.6H2O=266.3. 

Strontianite,  in  powder 1000  Gm 

Hydrochloric  acid  (32%.  of  HC1) 1550  Gm 

Strontium   hydroxide    25  Gm 

Water    500  Gm 

Mix  the  powdered  strontianiteina  porcelain  dish  with  the  water. 
Heat  the  mixture  to  about  60°.  Stir  well.  Add  the  acid  in  sev- 
eral portions,  waiting  after  each  addition  until  the  effervescence 
has  subsided  before  adding  more.  When  all  of  the  acid  has  been 
added  heat  to  boiling  for  half  an  hour.  Then  add  the  strontium 
hydroxide  and  stir  well.  The  solution  should  be  alkaline  in  reac- 
tion ;  if  it  is  not,  add  more  of  the  strontium  hydroxide  to  produce 
an  alkaline  reaction.  Keep  the  liquid  hot  for  an  hour  longer, 
stirring  frequently.  Then  filter.  Add  enough  hydrochloric  acid 
to  the  filtrate  to  render  it  acid.  Evaporate  to  1.30  sp.  w.  Set  it 
aside  to  cool  and  crystallize.  Drain  and  dry  the  crystals. 

The  mother-liquor  yields  more  salt  on  evaporation  in  the  usual 
way. 

Reaction.    SrCO;:+2HCl= SrCL+H2O+CO2. 


STRONTIUM      CHLORIDE.  6ll 

Notes.  The  strontium  chloride  thus  obtained  is  not  pure.  The 
principal  impurity  is  barium  chloride,  for  the  strontianite  contains 
barium  carbonate.  Calcium  salt  is  also  contained  in  the  product. 

It  may  be  partially  purified  as  follows  : 

Dissolve  it  in  water.  Add  enough  ammonia  water  to  impart 
an  alkaline  reaction  on  litmus  paper.  Stir  well.  Filter.  Add 
enough  diluted  sulphuric  acid  to  the  filtrate  to  render  the  liquid 
decidedly  acid  in  reaction.  Let  stand  for  two  days.  Filter.  Add 
enough  pure  strontium  carbonate  to  neutralize  the  free  acid  and 
leave  an  excess  of  strontium  carbonate  undissolved.  Set  the  mix- 
ture in  a  warm  place  for  a  day.  Filter  again.  Evaporate  the 
filtrate  tc  dryness.  Dissolve  the  residue  in  three  times  its  weight 
of  water,  filter,  and  evaporate  to  crystallization. 

The  barium  chloride  may  also  be  partially  precipitated  from  the 
solution  of  strontium  chloride  by  the  addition  of  alcohol  in  which 
strontium  chloride  is  soluble  while  the  barium  chloride  is  insoluble 
in  it.  Or  the  strontium  chloride  may  be  dissolved  in  alcohol,  the 
solution  filtered  and  evaporated  to  dryness,  the  salt  being  then  re- 
crystallized  from  a  water  solution. 

Description.  —  Long,  colorless,  deliquescent  crystals,  readily  sol- 
uble in  water  and  in  alcohol. 

STRONTIUM  HYDROXIDE. 

STRONTII     HYDROXIDUM. 

Sr(OH)2.8H2O=:265.5o. 

Add  8  parts  of  water  to  5  parts  of  the  oxide.  A  solid  crystalline 
mass  is  formed.  Dissolve  this  in  40  parts  of  boiling  water  ;  filter 
hot  ;  let  the  filtrate  cool  slowly.  Collect  and  dry  the  crystals. 

Description.  —  Transparent,  colorless,  deliquescent  crystals. 
STRONTIUM    IODIDE. 

STRONTII     IODIDUM. 


May  be  prepared  from  iron  iodide  and  strontium  hydroxide  (see 
Calcium  Iodide,  p.  326). 


6l2  STRONTIUM     IODIDE. 

Description. — Colorless,  transparent  plates ;  odorless ;  taste 
saline,  bitterish.  Deliquescent.  Becomes  yellow  on  exposure  to 
air  and  light.  Soluble  in  0.6  part  of  water  at  15°,  and  in  0.27 
part  of  boiling  water.  Also  soluble  in  alcohol. 

Must  be  kept  in  tightly-closed  bottles,  protected  against  light 


STRONTIUM   LACTATE. 

STRONTII     LACTAS. 

Sr(C3H503)2.3H20=3i9. 

Strontium   carbonate I  part 

Lactic  acid,  sufficient. 

Place  the  strontium  carbonate  together  with  5  parts  of  distilled 
water  in  a  porcelain  dish  over  a  water-bath.  Add  the  lactic  acid 
gradually,  stirring  constantly,  until  but  little  of  the  strontium  car- 
bonate remains  undissolved.  Continue  heating  the  mixture  at  the 
maximum  heat  of  the  bath,  until  the  lactic  acid  it  saturated, 
adding,  if  necessary,  a  little  more  strontium  carbonate  so  as  to 
have  a  sufficient  excess  to  insure  complete  neutralization.  Let 
the  liquid  cool,  filter  it,  and  evaporate  it  at  a  temperature  of  be- 
tween 60°  and  80°  C.  until  a  crystalline  mass  is  formed  on  cool- 
ing. Dry  the  product  in  a  current  of  air  without  the  aid  of  heat. 

Keep  it  in  well-stoppered  bottles. 

Description. — A  white,  granular  powder ;  odorless ;  taste  saline, 
slightly  bitter.  Soluble  in  4  parts  of  water  at  15°  ;  in  less  than 
one-half  its  weight  of  boiling  water.  Also  soluble  in  alcohol. 

STRONTIUM    NITRATE. 

STRONTII     NITRAS. 
Sr(N03)2=2II.5. 

Strontianite,  in  powder 200  parts 

Nitric  acid  (68%  of  HNO3) 250  parts 

Strontium  hydroxide 5  parts 

Water    300  parts 


STRONTIUM     NITRATE.  613 

Mix  the  strontianite  with  the  water.  Warm  the  creamy  mixture. 
Add  the  nitric  acid  gradually,  stirring  well  and  taking  care  not 
to  allow  the  liquid  to  run  over  from  a  too  violent  effervescence. 
When  all  of  the  acid  has  been  added,  heat  the  liquid  to  expel  the 
carbon  dioxide.  Add  the  strontium  hydroxide,  stir  well,  and 
digest  for  an  hour,  stirring  frequently.  Filter.  Acidify  the  fil- 
trate with  nitric  acid.  Evaporate  nearly  to  dryness,  and  place  the 
wet  crystalline  mass  of  salt  in  a  funnel  to  drain.  Dry  the  product 
with  the  aid  of  moderate  heat. 

Reaction.     SrCO3+  2HNO8=Sr(NO3)2+H2O+CO2. 

Description.  —  Transparent,  anhydrous  crystals,  readily  soluble 
in  water. 

STRONTIUM   OXIDE. 

STRONTII     OXIDUM. 


Prepared  by  strongly  heating  anhydrous  strontium  nitrate  to 
redness  for  an  hour  or  two. 

Reaction.     2Sr(NO3)2+2SrO+2N2O4+O2. 

Description.  —  A  dirty-white  porous  solid,  or  a  white,  amorphous, 
odorless  powder  of  caustic,  alkaline  taste. 
Must  be  kept  in  tightly-closed  bottles. 


SULPHUR. 

Sublimed  sulphur  contains  usually  some  arsenic  and  free  sul- 
phuric acid.     It  is  purified  as  follows : 

Washed  Sulphur. 

SULPHUR     LOTUM. 

Sublimed  sulphur 100  Gm 

Ammonia  water   10  ml 

Water,  sufficient. 

Add  the  sulphur  to  100  ml  of  water  previously  mixed  with  the 


614  SULPHUR. 

ammonia  water,  and  digest  for  three  days,  agitating  occasionally. 
Then  add  100  ml  of  water,  transfer  the  mixture  to  a  muslin 
strainer,  and  wash  the  sulphur  with  water  until  the  washings 
cease  to  give  an  alkaline  reaction  on  test-paper.  Then  drain,  press 
strongly,  dry  it  at  not  over  40°  C.  (104°  F.),  and  powder  by 
running  it  through  a  No.  30  sieve. 

Notes.  The  object  of  this  process  is  to  neutralize  and  wash 
away  the  sulphuric  acid  which  is  always  present  with  sublimed 
sulphur,  and  the  digestion  for  three  days  is  intended  to  remove 
also  any  arsenic  present.  To  effect  the  extraction  of  the  arsenic, 
continued  digestion  is  required,  and  three  days  is  not  too  long,  as 
the  ammonia  is  very  diluted.  Care  should  be  taken,  however, 
not  to  use  higher  heat  than  40°  C.  (104°  F.),  because  above  that 
"temperature  a  good  deal  of  ammonium  hydrosulphide  may  be 
formed,  and  at  the  boiling  point  the  sulphur  will  dissolve  as  long 
as  sufficient  ammonia  remains  to  act  upon  it.  Boiling  water  is, 
therefore,  not  to  be  used.  It  is  under  all  circumstances  necessary 
to  wash  out  all  the  ammonia  and  ammonium  salt  from  the  sulphur 
before  drying  it. 

It  is  important  to  dry  the  washed  sulphur  thoroughly  before 
putting  it  in  its  receptacle,  for  the  presence  of  any  moisture  would 
result  in  the  formation  of  sulphuric  acid  again,  rendering  a  repeti- 
tion of  the  washing  necessary. 

Reaction.     As2S3+H2SO4+  6H4NOH= 
(H4N)2S04+(H4N) 


Description.  —  A  fine,  yellow,  odorless  and  tasteless  powder.  In- 
soluble in  water  and  in  official  alcohol. 

Precipitated  Sulphur. 

SULPHUR    PRAECIPITATUM. 

Sublimed   sulphur    .....................   2  parts 

Lime    ................................    i  part 

Official  hydrochloric  acid,  water,  each  sufficient. 

Slake  the  lime  and  make  it  into  a  uniform  mixture  with  10  parts 
of  water.  Add  the  sulphur,  previously  well  dried  and  sifted,  mix 
well,  add  25  parts  of  water,  and  heat  the  mixture  to  boiling  for 


SULPHUR.  615 

one  hour,  stirring  constantly,  and  replacing-  the  water  lost  by 
evaporation.  Then  cover  the  vessel,  allow  the  contents  to  cool, 
pour  off  the  clear  solution,  filter  the  remainder,  and  unite  the 
liquids. 

Add  gradually  hydrochloric  acid  previously  diluted  with  an 
equal  volume  of  water,  until  the  liquid  is  nearly  neutralized,  being 
careful  to  leave  it  still  distinctly  alkaline  in  reaction  and  of  yellow 
color. 

Collect  the  precipitate  on  a  strainer,  and  wash  it  with  water 
until  the  washings  are  tasteless  and  no  longer  give  an  acid  reac- 
tion on  test-paper.  Then  dry  it  at  a  gentle  heat. 

Reactions.  The  lime  is  first  slaked,  CaO-f  H2O— Ca(OH)2. 
Then,  when  sulphur  is  boiled  with  the  calcium  hydroxide,  the  fol- 
lowing reaction  occurs:  3Ca(OH)2-f-i2S=2CaSS4+GaS2O3+ 
3H2O.  The  solution,  containing  calcium  tetrathiosulphate  and 
calcium  thiosulphate,  is  next  treated  with  hydrochloric  acid,  when 
sulphur  is  precipitated:  CaSS4+2HCl:=CaCl2+4S+H2S. 

Notes.  The  quantity  of  lime  used  is  purposely  somewhat  in  ex- 
cess of  the  amount  required  by  theory,  to  make  up  for  carbonate 
contained  in  it.  A  larger  excess  would,  however,  result  in  loss 
because  the  compounds  then  formed  would  yield  larger  quantities 
of  H2S  when  the  hydrochloric  acid  is  added. 

By  long  boiling  the  calcium  mono-thiosulphate  is  split  up  into 
sulphite  and  sulphur.  A  portion  of  the  sulphite  is  oxidized  to  sul- 
phate, which  is  precipitated. 

If  the  first  portion  of  hydrochloric  acid  is  added  very  slowly  no 
hydrogen  sulphide  is  formed,  because  the  reaction  then  is: 
2CaSS4+2HCl=Ca612+Ca(SH)2+4S2.  When  more  acid  is 
added,  however,  the  reaction  just  described  is  followed  by: 
Ca  ( SH )  2+2HCl==CaCl2+2H2S. 

The  directions  of  the  Pharmacopoeia  are  to  only  "nearly"  neu- 
tralize the  solution,  and  to  be  careful  to  leave  it  slightly  alkaline. 
The  object  of  this  precaution  is  to  prevent  the  precipitation  of 
any  arsenic  present.  The  calcium  thiosulphate  is  not  decomposed 
unless  enough  hydrochloric  acid  be  added  to  impart  an  acid  reac- 
tion to  the  liquid.  Hence  the  sulphur  which  enters  into  the 
structure  of  the  calcium  thiosulphate  is  lost.  But  if  enough  hy- 
drochloric acid  be  added  to  decompose  the  thiosulphate  (2CaSS4 
+CaSO3S+6HCl=3CaCl2+i2SL,+3H,.O),  the  arsenic  will  also 


6l6  SULPHUR. 

be  precipitated  as  follows  :  Ca3(AsSJ2+6HCl=As2S3+3H2S+ 
3CaCl2+2S. 

When  the  liquid  is  alkaline,  however,  all  of  the  arsenic  remains 
in  solution. 

Care  should  be  taken  to  arrange  so  that  the  hydrogen  sulphide 
gas  is  led  off  through  a  flue,  or  the  operation  should  be  carried 
out  in  the  open  air.  The  gas  is  evolved  in  large  enough  quantities 
to  be  very  annoying  to  the  operator. 

The  acid  must  be  added  to  the  solution  of  the  sulphur  salts  and 
not  vice  versa;  moreover,  the  acid  must  be  diluted  as  directed; 
otherwise  an  oily  product  (H2S2?)  is  formed  which  afterwards 
is  difficult  to  eliminate  and  which  but  slowly  decomposes,  giving 
off  H2S. 

The  well-washed'  precipitated  sulphur  must  be  rapidly  but 
thoroughly  dried  at  a  moderate  heat  and  kept  in  tightly-closed 
bottles. 

Description.  —  An  odorless  and  tasteless,  pale-yellowish,  fine 
powder,  insoluble  in  water  ;  readily  soluble  in  carbon  disulphide  ; 
also,  soluble  in  ether,  chloroform,  fixed  oils  and  volatile  oils,  ben- 
zin,  and  benzol.  Melts  at  115°  C,  and  at  a  higher  heat  volatilizes 
without  residue,  or  burns  in  the  air  forming  sulphur  dioxide. 

SULPHUR    DIOXIDE. 

SULPHURIS      DIOXIDUM. 


Copper  turnings  or  scraps  .............    100  Gm 

Concentrated  sulphuric  acid   ...........   300  Gm 

Water    ..............................    100  Gm 

Put  the  sulphuric  acid  in  a  porcelain  dish  of  about  one 
liter's  capacity  ;  set  the  acid  into  rapid  whirling  motion  by  cir- 
culatory stirring  in  one  direction  with  a  glass  rod.  Then  slowly 
pour  the  water  into  the  acid,  continuing  the  stirring  uninterrupt- 
edly until  all  the  water  has  been  added. 

Put  the  copper  into  a  round-bottomed  flask  of  about  one  and 
one-half  liter's  capacity.  Provide  the  flask  with  a  twice  perforated 
rubber  stopper  carrying  a  thistle  tube  and  a  delivery  tube.  Con- 
nect the  delivery  with  a  wash-bottle  of  about  one-half  liter's 


SULPHUR     DIOXIDE.  617 

capacity  containing  about  200  Cc.  of  water  and  provided  with  a 
thrice  perforated  rubber  stopper  carrying  a  thistle  tube  and  second 
delivery  tube  with  connections  by  means  of  which  the  sulphur 
dioxide  may  be  conducted  into  any  desired  receiver. 

Add  the  mixture  of  sulphuric  acid  and  water  to  the  copper,  and, 
having  inserted  the  stoppers  and  fittings  and  completed  all  con- 
nections, heat  the  flask  until  the  reaction  begins.  Then  remove 
the  burner  from  under  the  flask  so  long  as  the  reaction  continues 
briskly,  applying  heat  again  only  when  the  evolution  of  sulphur 
dioxide  becomes  too  slow. 

Reaction.    Cu+2H2SO4=CuSO4+2H2O+SO2. 

Notes.  It  will  be  seen  that  a  large  excess  of  copper  is  pre- 
scribed; this  is  to  facilitate  the  evolution  of  the  gas.  The  heat 
generated  by  the  reaction  itself,  after  it  has  been  started  by  the 
application  of  heat  from  without,  is  sufficient  to  maintain  the  action 
for  some  time.  A  strong  dish  should  be  placed  under  the  flask 
while  the  reaction  proceeds  without  the  use  of  the  burner,  so  that, 
if  the  flask  should  break,  its  contents  may  be  caught  in  the  dish. 

When  the  acid  is  saturated  the  copper  sulphate  formed  in  the 
flask  may  be  dissolved  in  water  and  recovered  by  crystallization. 

The  amount  of  sulphuric  acid  ordered  will  furnish,  when  en- 
tirely consumed,  about  90  to  96  Gm  of  SO2. 

Sulphur  dioxide  may  be  conveniently  prepared  in  this  way  when 
required  for  making  sulphurous  acid  and  water-soluble  sulphites, 
and  for  other  purposes.  Larger  quantities  of  the  materials  and 
apparatus  of  greater  capacity  are,  of  course,  to  be  employed  when 
requisite. 

Sulphur  dioxide  may  also  be  prepared  by  heating  sulphuric 
acid  with  charcoal,  and  this  method  is  prescribed  by  the  Pharma- 
copoeia for  the  preparation  of  sulphurous  acid.  It  is  economical, 
because  all  of  the  sulphuric  acid  decomposed  yields  SO.,,  whereas 
the  copper  process  involves  the  formation  of  copper  sulphate 
which  consumes  one-half  of  the  sulphuric  acid  decomposed.  If 
the  copper  sulphate  is  recovered,  however,  the  difference  in  cost  is 
insignificant.  But  the  method  of  generating  sulphur  dioxide  by 
reducing  sulphuric  acid  by  heating  this  with  carbon  can  not  be 
employed  in  cases  where  the  carbon  dioxide  formed  in  that  process 
is  objectionable. 


6l8  SULPHUR  IODIDE. 

SULPHUR  IODIDE. 

SULPHURIS  IODIDUM. 

Consists  chiefly  of  S2I2= 


Washed   sulphur.  .  .  ....................    I  part 

Iodine  ................................   4  parts 

Mix  them  thoroughly  by  trituration  in  a  glazed  porcelain  mor- 
tar (or  in  a  glass  mortar).  Put  the  mixture  into  a  flask,  beaker 
or  wide-mouthed  bottle,  close  the  top  loosely,  and  apply  gentle 
heat  (not  exceeding  60°  C.)  by  means  of  a  water-bath  until  the 
elements  combine,  which  is  known  by  the  fact  that  the  mass  as- 
sumes a  uniformly  dark  color.  Then  raise  the  temperature  until 
the  mass  becomes  liquid.  Pour  the  fused  sulphur  iodide  upon 
a  porcelain  tile  or  plate  or  upon  any  other  convenient  cold  surface 
not  affected  by  it.  Break  the  cake,  when  cool,  into  small  pieces 
and  transfer  the  product  to  small  glass-stoppered  bottles. 

Must  be  kept  in  a  cool  place. 

Notes.  The  sulphur  and  iodine,  when  previously,  intimately 
mixed,  combine  easily.  The  compound  S2I2  is,  however,  not 
stable.  If,  during  the  process  of  heating  the  iodine  and  sulphur 
together,  or  in  the  fusion  of  the  iodide,  any  portion  of  the  iodine 
should  become  volatilized  and  condense  upon  the  sides  or  in  the 
upper  part  of  the  container  in  which  the  reaction  is  performed, 
this  iodine  must  be  returned  to  the  liquid  portion  by  bringing  it 
in  contact  with  the  fused  mass,  which  is  easily  accomplished  by 
inclining  the  container  in  the  direction  required.  Full  water-bath 
heat  is  sufficient  to  effect  the  liquefaction  of  the  product.  The 
flask  or  other  vessel  in  which  the  iodide  of  sulphur  is  made  may 
be  covered  with  a  watch  crystal  during  the  operation. 

Description.  —  A  brittle,  grayish-black,  crystalline  solid  of  some- 
what metallic  lustre,  having  an  odor  of  iodine  and  an  acrid  taste. 
Insoluble  in  water  ;  soluble  in  60  parts  of  glycerin.  Decomposed 
by  alcohol  and  ether,  which  dissolve  the  iodine,  leaving  the  sul- 
phur. It  loses  iodine  on  exposure.  Decomposes  when  heated 
long  or  to  a  high  temperature  ;  but  it  should  leave  no  residue  on 
volatilization. 


TIN     CHLORIDE. 

TIN    CHLORIDE. 

STANNI    DICHLORIDUM. 

(Stannous  Chloride.     Tin  Salt.) 
SnCl2.2H2O=225.8. 

Tin,  granulated 100  parts 

Hydrochloric  acid  (35%  of  HC1) 175  parts 

Dissolve  the  tin  in  the  hydrochloric  acid  by  digestion.  Finally 
heat  at  about  60°  until  all  action  ceases  and  the  acid  is  saturated. 
Let  cool  and  settle.  Decant  the  clear  solution  and  evaporate  it  to 
the  sp.  w.  of  1.985.  Then  set  it  aside  in  a  covered  dish  to  crystal- 
lize. Drain  the  crystals  well  in  a  covered  funnel,  and  dry  the 
product  in  a  desiccator  over  sulphuric  acid.  Bottle  the  salt  as 
soon  as  dry. 

Reaction.     Sn+2HCl=SnCl2+H2. 

Description. — Colorless  crystals,  soluble  in  0.37  part  of  water  at 
15°.  Decomposed  by  more  water. 

ZINC   ACETATE. 

ZINCI     ACETAS. 

Zn(C2H3O2)2.2H20=2i9.3. 

Zinc  oxide    300  Gm 

Acetic  acid   1000  ml 

Distilled  water 1000  ml 

Mix  600  ml  of  the  acid  with  the  whole  of  the  water  in  a  flask, 
add  the  zinc  oxide,  agitate  gently,  and  warm  the  mixture  to  about 
60°  C. ;  add  the  remainder  of  the  acid  gradually,  continuing  the 
digestion  until  no  more  of  the  oxide  is  dissolved.  Heat  the  solu- 
tion to  the  boiling  point ;  filter  while  hot,  add  a  little  acetic  acid 
(about  10  ml)  to  insure  that  the  acid  is  present  in  slight  excess. 
Set  the  solution  in  a  cool  place  for  two  days  to  crystallize.  De- 
cant the  mother-liquor,  evaporate  it  over  a  water-bath  to  one-half, 
acidulate  with  acetic  acid  as  before,  if  necessary,  and  again  set 


62O  ZINC     ACETATE. 

aside  to  crystallize  in  a  cool  place.  Put  the  crystals  in  a  funnel 
to  drain ;  then  dry  them  on  filter  paper  or  on  a  porous  tile,  with- 
out the  aid  of  heat. 

Must  be  kept  in  a  tightly-corked  bottle. 

Reaction.     ZnO+2HC2H3O2=Zn(C2H3O2)2+H2O. 

Notes.  The  same  result  will  be  obtained  if  420  Gm  of  zinc 
carbonate  be  used  instead  of  300  Gm  of  the  oxide.  The  carbonate 
should  be  added  gradually  on  account  of  the  effervescence  caused 
by  the  liberation  of  carbonic  acid,  and  the  solution  formed  is  then 
to  be  boiled  a  few  minutes  to  expel  the  carbonic  acid  perfectly. 

When  the  preparation  is  made  on  a  manufacturing  scale  from 
commercial  zinc  oxide  or  carbonate,  it  is  necessary  to  digest  the 
solution  of  acetate  of  zinc  for  several  days  with  some  pure  metallic 
zinc,  or  with  pure  zinc  oxide,  in  order  to  remove  any  lead,  copper, 
cadmium  and  iron  that  may  be  present.  By  this  digestion,  how- 
ever, some  basic  zinc  acetate  is  formed,  which  must  be  converted 
into  normal  acetate  by  the  addition  of  more  acetic  acid  before 
crystallizing.  A  solution  of  basic  salt  will  not  crystallize,  but  the 
presence  of  a  little  free  acetic  acid  facilitates  the  crystallization. 

When  the  first  crop  of  crystals  has  been  collected,  the  mother- 
liquor  must  be  evaporated  at  a  temperature  not  above  80°  C. 
(176°  F.)  until  a  pellicle  forms,  after  which  it  is  set  aside  in  a 
cool  place.  If  the  evaporation  is  carried  too  far  a  precipitate  of 
zinc  acetate  containing  but  one  molecule  of  water  of  crystalliza- 
tion will  deposit. 

Zinc  acetate  may  also  be  made  by  double  decomposition  from 
38  parts  of  lead  acetate  and  29  parts  of  zinc  sulphate,  each  dis- 
solved in  80  parts  of  distilled  water,  the  solutions  being  filtered 
and  then  mixed.  The  reaction  is  then : 

Pb(C2H;A)2+ZnSO4=Zn(CH3O2)2+PbSO4. 

Description. — Soft,  white,  pearly  crystals,  of  a  faintly  acetous 
odor  and  an  astringent,  afterwards  metallic  taste.  Soluble  in  2.7 
parts  of  water  and  in  36  parts  of  alcohol  at  15°  ;  in  1.5  parts  of 
boiling  water,  and  in  3  parts  of  boiling  alcohol.  Reaction  acid. 


ZINC      BROMIDE.  621 

ZINC    BROMIDE. 

ZINCI     BROMIDUM. 


Zinc  sulphate  .........................   8  parts 

Potassium  bromide  ....................   7  parts 

Boiling  distilled  water,  sufficient. 

Dissolve  the  sulphate  in  10  parts  and  the  bromide  in  6  parts  of 
the  water.  Mix  the  solutions  while  hot.  When  cool  add  40  parts 
of  alcohol,  and  filter  the  mixture  through  asbestos.  Evaporate 
the  filtrate  to  dryness,  and  granulate  the  product. 

Reaction.     ZnSO4+2KBr=K2SO4-f  ZnBr2. 

Zinc  bromide  may  also  be  made  from  zinc  sulphate  and  barium 
bromide. 

Another   Method. 

Zinc    ...............................     66  parts 

Bromine    ...........................    160  parts 

Water    .............................   250  parts 

Put  the  zinc  and  water  in  a  flask  of  about  500  Cc.  capacity.  Add 
the  bromine  in  small  portions  at  a  time,  waiting  after  each  addi- 
tion until  the  red  color  has  nearly  disappeared  and  the  reaction 
subsided.  When  all  of  the  bromine  has  been  added,  filter  the 
liquid  and  evaporate  to  dryness. 

Description.  —  A  white,  granular  salt  ;  odorless  ;  of  sharp,  saline, 
metallic  taste  Very  hygroscopic.  Readily  soluble  in  water  and 
in  alcohol. 

ZINC   CARBONATE;     PRECIPITATED. 

ZINCI     CARBONAS     PRAECIPITATUS. 

2ZnCO,.3Zn(OH)2=548.5. 

Zinc  sulphate   ........................   20  parts 

Sodium  carbonate   ....................   21  parts 

Boiling  water,  sufficient. 


622  ZINC     CARBONATE. 

Dissolve  the  sodium  carbonate  in  40  parts  of  the  water  in  a 
porcelain  capsule.  Dissolve  the  zinc  sulphate  in  an  equal  quantity 
of  boiling  water.  Place  the  capsule  containing  the  solution  of 
sodium  carbonate  on  a  sand-bath  so  as  to  keep  the  solution  hot  ; 
then  gradually  add  the  solution  of  zinc  sulphate,  stirring  briskly. 
Boil  the  mixture  for  fifteen  minutes  after  the  effervescence  has 
ceased  ;  then  let  the  precipitate  subside.  Decant  the  mother-liquor 
and  throw  it  away.  Add  120  parts  of  boiling  water  to  the  precip- 
itate, and  stir  well,  let  settle  once  more,  and  repeat  the  washing 
by  affusion  and  decantation  of  hot  distilled  water  until  the  wash- 
ings cease,  to  give  any  precipitate  with  test  solution  of  barium 
chloride.  Collect  the  precipitate  on  a  muslin  strainer  or  on  a 
paper  filter,  let  it  drain  thoroughly,  and  then  dry  it  at  a  gentle 
heat. 

Reaction. 

5Na2C03+5ZnS04+3H20 

« 

=2ZnCO3.3Zn(OH)2+5Na2SO4+3CO2. 

Notes.  The  solutions  are  used  hot  in  order  to  expel  all  the  car- 
bonic acid  which  is  set  free,  carbon  dioxide  escaping  with  effer- 
vescence. If  cold  solutions  are  used  a  portion  of  the  precipitate 
redissolves  in  the  carbonic  acid  held  in  the  liquid.  The  zinc  sul- 
phate is  to  be  added  to  the  sodium  carbonate  in  order  to  keep  the 
latter  in  excess,  and  by  having  the  soda  solution  hot,  the  further 
advantage  is  gained  that  the  precipitate  is  more  readily  washed 
free  from  sodium  salt. 

Description.  —  A  fine,  white,  odorless  and  tasteless,  insoluble 
powder. 

ZINC   CHLORIDE. 

ZINCI     CHLORIDUM. 


A  solution  of  zinc  chloride  is  prepared  as  described  in  the 
article  below.  It  is  then  evaporated  to  dryness  and  the  residue 
fused,  or  the  product  is  granulated.  It  must  be  bottled  while 


ZINC     CHLORIDE.  623 

warm  in  warm  dry  bottles,  and  should  be  kept  in  small,  tightly- 
stoppered  bottles. 

Description. — Zinc  chloride  should  be  perfectly  white.  It  is 
very  deliquescent.  Its  solution  is  strongly  acrid,  corrosive,  and 
of  acid  reaction. 

Zinc  Chloride  Solution. 

LIQUOR    ZINCI  CHLORIDi;  U.   S. 

The  official  solution  of  zinc  chloride  (U.  S.  P.,  1890)  contains 
about  50  per  cent  of  ZnCl2.  It  is  prepared  as  follows : 

Granulated  zinc   240  Gm 

Hydrochloric  acid   840  Gm 

Nitric  acid    12  Gm 

Precipitated  zinc  carbonate   12  Gm 

Distilled  water,  sufficient. 

Put  the  zinc  in  a  glass  or  porcelain  vessel,  and  add  150  ml  of 
distilled  water.  Then  add  the  hydrochloric  acid  gradually.  Di- 
gest until  the  acid  shall  have  become  saturated.  Decant  the  solu- 
tion from  the  undissolved  excess  of  zinc. 

Add  the  nitric  acid  to  the  solution,  evaporate  the  mixture  to 
dryness  and  heat  the  dry  mass  to  fusion  at  a  temperature  not  ex- 
ceeding 115°  C. 

Let  the  fused  zinc  chloride  cool  and  then  dissolve  it  in  a  suffi- 
cient quantity  of  distilled  water  to  make  the  weight  of  the  solution 
one  thousand  grams. 

Add  the  precipitated  zinc  carbonate,  agitate  the  mixture  occa- 
sionally during  twenty-four  hours,  and  then  set  it  aside,  at  rest, 
until  clarified  by  subsidence. 

Finally  separate  the  clear  solution  by  decantation  or  by  means 
of  a  glass  syphon,  and  keep  it  in  glass-stoppered  bottles. 

Reaction.     Zn-f2HCl=ZnCl2-f  H2. 

Notes.  The  metal  dissolves  in  the  hydrochloric  acid  with  the 
liberation  of  heat  and  the  evolution  of  hydrogen.  Instead  of 
adding  the  acid  to  the  zinc,  the  metal  may  be  added  to  the  acid. 

The  effervescence  caused  by  the  escape  of  the  hydrogen  may 
be  very  active  at  first,  but  subsides  as  the  zinc  chloride  increases 
and  the  acid  diminishes.  When  but  little  acid  remains  digestion 


624  ZINC     CHLORIDE. 

is  necessary  to  cause  complete  saturation,  and  further  digestion 
is  desirable  to  cause  the  separation  of  certain  foreign  metals  which 
may  have  been  contained  in  the  zinc. 

Commercial  zinc  is  usually  contaminated  with  one  or  more  of 
the  metals,  copper,  lead,  arsenic,  cadmium,  iron  and  manganese. 
When  an  excess  of  zinc  is  used,  so  that  a  portion  of  it  remains 
undissolved  at  the  end  of  the  digestion,  several  of  these  other 
metals  dissolved  together  with  the  zinc  are  precipitated  by  the 
latter  on  prolonged  digestion. 

But  one  of  the  most  common  impurities  is  iron,  which  can  not 
be  precipitated  by  digestion  with  an  excess  of  zinc.  To  remove 
the  iron  (and  manganese)  nitric  acid  is  added  to  convert  the 
ferrous  chloride  to  ferric,  and  the  solution  is  evaporated  to  dry- 
ness  and  the  residue  fused  to  expel  the  excess  of  nitric  acid.  The 
fused  zinc  chloride  (containing  any  iron  chloride  derived  from 
the  iron  in  the  zinc  used)  is  then  redissolved  and  the  solution 
shaken  with  precipitated  zinc  carbonate,  which  removes  the  iron 
which  is  precipitated  in  the  form  of  hydroxide. 

Solution  of  zinc  chloride  cannot  be  filtered  through  paper,  be- 
cause the  latter  swells  until  its  pores  are  closed  and  is  then  cor- 
roded. It  may  be  filtered  through  powdered  and  washed  glass, 
or  through  purified  asbestos.  Decantation  is  sometimes  suffi- 
cient. A  dilute  solution  may  be  filtered  through  paper,  but  the 
organic  substances  then  taken  up  by  it  blacken  the  product  as 
soon  as  sufficiently  concentrated  by  evaporation. 

Description. — A  clear,  colorless,  odorless  liquid  of  astringent, 
sweetish,  metallic  taste  and  acid  reaction.  Corrosive  in  its  action 
upon  organic  matter.  Sp.  w.  about  1.535  at  I5°- 

ZINC   CYANIDE. 

ZINCI    CYANIDUM. 

Zn(CN)  ,=.117.3. 

Prepared  by  precipitating  a  solution  of  zinc  acetate  with  hydro- 
cyanic acid. 

Description. — A  colorless  salt,  insoluble  in  water  and  in  alcohol, 
but  soluble  in  solutions  of  alkalies  with  which  it  forms  water- 
soluble  double  salts. 


ZINC     IODIDE.  625 


ZINC  IODIDE. 

ZINCI     IODIDUM. 


Granulated  zinc  .....  .  ................     3  parts 

Iodine    ..............................    10  parts 

Distilled   water    ......................   20  parts 

Digest  together  in  a  flask  until  colorless  and  free  from  the  odor 
of  iodine.  Filter  through  asbestos  or  powdered  glass,  and  evap- 
orate the  filtrate  rapidly  to  dryness  at  a  moderate  heat. 

Must  be  kept  in  small  well-closed  vials. 

Description.  —  A  white,  granular  salt  ;  odorless  ;  taste  sharp, 
saline,  metallic.  Very  hygroscopic.  Readily  soluble  in  water, 
alcohol  and  ether. 

ZINC  LACTATE. 

ZINCI     LACTAS. 

Zn(C3H503)2.3H20=297.3. 

Prepared  by  neutralizing  warm  dilute  lactic  acid  with  zinc  car- 
bonate, and  crystallizing. 

Can  also  be  prepared  by  double  decomposition  between  sodium 
lactate  and  zinc  chloride. 

Description.  —  White  or  colorless  quadrangular  crystals,  inodor- 
ous, and  having  an  acidulous  metallic  taste,  and  acid  reaction. 
Soluble  in  58  parts  of  cold  and  6  parts  of  boiling  water  ;  nearly 
insoluble  in  alcohol. 

ZINC  OLEATE. 

ZINCI    OLEAS. 


Zinc   acetate  .....  ......................   2  parts 

Powdered  white  castile  soap  .............   5  parts 

Dissolve  the  zinc  acetate  in  300  parts  of  water,  and  the  soap  in 

11—40 


626  ZINC     OLEATE. 

200  parts  of  hot  water.  Add  the  cold  soap  solution  to  the  solu- 
tion of  zinc  acetate,  stirring  briskly.  Drain  the  precipitated  zinc 
oleate  on  a  muslin  strainer,  and  wash  it  several  times  with  cold 
water.  Dry  it  on  paper  or  muslin,  without  the  aid  of  heat. 

Reaction.  2NaC18H83O2+Zn  ( C2H3O2 )  2=Zn  ( C18H83O2 )  2+ 
2NaC2H302. 

Notes.  The  sodium  acetate  is  easily  washed  away  from  the 
precipitated  oleate.  The  yield  is  about  2.4  parts. 

Description. — A  soft,  white  powder,  having  a  soapy  feel. 

Another  Method. 

Zinc  sulphate   3  parts 

Powdered  Castile  soap 5  parts 

Dissolve  the  zinc  sulphate  in  300  parts  of  water,  and  the  soap  in 
200  parts  of  hot  water.  Keep  the  soap  solution  at  the  temperature 
of  about  40°,  and  add  to  it  slowly  and  with  brisk  stirring,  the 
solution  of  zinc  sulphate.  Collect  the  precipitate  on  a  muslin 
strainer,  wash  it  with  water  of  40°  temperature,  drain  it  well,  and 
dry  it  at  not  over  40°.  Pass  the  dried  friable  mass  through  a 
sieve. 

OfUcial  Zinc  Oleate. 

Zinc  oxide    5  parts 

Oleic  acid  95  parts 

Put  the  oleic  acid  in  a  roomy  porcelain  dish,  and  sift  the  zinc 
oxide  into  the  acid,  stirring  well  so  as  to  mix  the  two  thoroughly 
and  avoid  the  formation  of  lumps.  Let  the  mixture  stand  several 
hours,  stirring  occasionally.  Then  heat  the  mixture  over  a  water- 
bath  until  the  oxide  is  completely  dissolved. 

Reaction.   ZnO+2HC18H83O2=Zn ( C18H33O2)  2+H,O. 

Notes.    If  the  quantities  operated  upon  are  small,  the  zinc  oxide, 


ZINC     OLEATE.  627 

previously  sifted,  may  well  be  mixed  with  the  oleic  acid  by  tritu- 
ration  in  a  mortar,  the  acid  being  gradually  added  to  the  oxide. 
The  mixture  should  be  allowed  to  stand  at  least  two  hours  before 
it  is  heated. 

It  will  be  observed  that  a  very  large  excess  of  oleic  acid  is  used, 
so  that  the  preparation  is  a  mixture  of  zinc  oleate  and  oleic  acid. 

The  zinc  oxide  used  must  be  quite  free  from  iron;  otherwise 
the  product  will  be  pinkish,  or  reddish,  or  yellowish,  according 
to  the  condition  and  amount  of  iron  in  it. 

Description. — A  soft,  white,  homogeneous  ointment  is  formed 
out  of  zinc  oxide  and  oleic  acid  when  the  percentage  of  zinc  oxide 
is  sufficient ;  with  less  zinc  oxide  the  product  is  fluid  or  semi-fluid. 
True  zinc  oleate,  without  an  excess  of  oleic  acid,  is  a  powder. 
The  official  zinc  oleate,  obtained  by  the  formula  here  given,  is  a 
soft  ointment. 

Pure  zinc  oleate  is  prepared  as  described  under  Zinci  Oleas. 


ZINC  OXIDE. 

ZINCI    OXIDUM. 

ZnO=8i.3. 

Calcine  the  official  zinc  carbonate  in  a  dish  at  a  low  red  heat 
until  a  cooled  sample,  mixed  with  a  little  water,  no  longer  effer- 
vesces with  diluted  hydrochloric  acid. 

Reaction.     2(ZnCO:0.3Zn(OH)2=5ZnO+3H2O+2CO2. 

Notes.  Too  high  heat  renders  the  product  yellow,  and  this 
yellowish  tint  may  be  retained  for  a  long  time.  [All  pure  zinc 
oxide  turns  yellow  when  heated  but  becomes  white  again  on  cool- 
ing unless  it  was  heated  too  strongly.  A  zinc  oxide  containing 
much  iron  is  always  discolored  even  if  not  overheated  in  the  proc- 
ess of  calcination.]  Overheating  also  makes  zinc  oxide  less  soft 
to  the  feel. 


628  ZINC     PHENOLSULPHONATE. 

ZINC  PHENOLSULPHONATE. 

ZINCI     PHENOLSULPHONAS. 

Zn(C6H5S04)2.8H20=555.3. 
( Sulphocarbolate  of  Zinc.) 

Crystallized  phenol   20  parts 

Sulphuric  acid 25  parts 

Barium  carbonate   40  parts 

Zinc  sulphate 29  parts 

Water. 

Add  the  phenol  to  the  acid,  mix  well,,  and  heat  the  mixture  at 
55°  in  a  porcelain  dish  over  a  water-bath  for  several  days.  Add 
400  parts  of  water  and  mix  well.  Then  neutralize  by  adding  the 
barium  carbonate,  stirring  the  whole  thoroughly.  Filter.  Reject 
the  precipitate.  To  filtrate  add  the  zinc  sulphate  previously  dis- 
solved in  200  parts  of  water.  Now  filter  away  the  precipitated 
barium  sulphate,  slightly  acidulate  the  filtrate  with  sulphuric  acid, 
and  evaporate  to  crystallization. 

Purify  the  product  by  repeated  re-crystallizations. 

Reactions.  2HC6H5SO4+BaCO3=Ba(C6H5SO4)2+H2O+ 
CO2;  and  then,  Ba(CeHBSO4)2+ZnSO4=Zn(C6H5SO4)2-j- 
BaSO4. 

Notes.  The  solution  of  zinc  sulphate  should  be  added  to  the 
solution  of  sulpho-carbolate  of  barium  until  exactly  precipitated— 
that  is,  the  further  addition  of  zinc  sulphate  must  be  discontinued 
as  soon  as  it  no  longer  causes  any  further  precipitation.  Sulpho- 
carbolate of  zinc  crystallizes  more  readily,  and  without  reddish 
color,  from  a  solution  acidulated  with  sulphuric  acid. 

Description. — Colorless  crystals,  readi1y  soluble  in  water  and  in 
alcohol. 


ZINC     SALICYLATE.  629 

ZINC  SALICYLATE. 

ZINCI  SALICYLAS. 


Zinc  oxide    ..........................     3  parts 

Salicylic  acid   ........................    10  parts 

Distilled  water,  sufficient. 

Mix  the  salicylic  acid  with  50  parts  of  water,  and  heat  the 
mixture.  Add  gradually  the  zinc  oxide  previously  mixed  with 
15  parts  of  water,  until  no  more  dissolves.  Filter,  and  set  aside 
to  crystallize. 

Description.  —  Colorless  crystals,  soluble  in  water  and  in  alcohol. 


ZINC  SULPHATE. 

ZINCI  SULPHAS. 

ZnH2SO5.6H2O=28;.3. 

Zinc  clippings,  or  granulated  zinc  ........  4  parts 

Sulphuric  acid  ........................   5  parts 

Dilute  the  acid  with  30  parts  of  water;  add  the  zinc  gradually. 
When  effervescence  has  ceased,  digest  with  the  undissolved  por- 
tion of  the  metal  for  a  few  days.  Filter.  Evaporate  the  filtrate 
until  a  drop  becomes  turbid  on  cooling.  Then  let  the  solution 
become  cold,  stirring  constantly  so  that  small  crystals  may  be 
formed.  Collect  and  dry  these  on  muslin.  Evaporate  the  mother- 
liquor  to  obtain  more  crystals. 

Reaction.     Zn-f  H2SO4+7H2O=ZnH,SO5.6H2O+H2. 

Notes.  The  zinc  should  be  nearly  free  from  other  metals.  If 
it  contains  iron,  the  zinc  sulphate  contaminated  with  ferrous  sul- 
phate will  become  yellow  in  time  by  the  oxidation  of  the  ferrous 
to  ferric  salt.  Zinc  sulphate  containing  iron  will,  of  course,  be 
unfit  for  the  preparation  of  zinc  oxide. 

Any  iron  and  manganese  present  in  the  metal  will  not  be  re- 


630  ZINC     SULPHATE. 

moved  by  digestion  with  an  excess  of  zinc ;  but  lead,  copper,  and 
cadmium,  if  present,  are  thus  separated.  The  gray  flocculi  which 
are  formed  when  the  zinc  is  dissolved  in  the  acid  are  mainly  lead. 

Pure  zinc  dissolves  with  difficulty  in  the  acid;  if  it  contains 
iron  it  dissolves  more  rapidly  in  proportion  to  the  iron  in  it. 

Iron  is  removed  as  described  below  in  the  recrystallization  of 
zinc  sulphate. 

The  solution  should  not  be  too  concentrated  for  crystallizing, 
for  when  the  salt  is  crystallized  from  a  warm  solution  (over 
30°  C.)  the  crystals  formed  contain  less  water  of  crystallization 
(ZnSO4-5H2O).  The  crystals  should  be  dried  without  the  aid  of 
heat,  or  at  least  at  a  temperature  not  exceeding  30°  C. 

Impure  zinc  sulphate  may  be  purified  to  a  great  extent  by  re- 
crystallization.  The  salt  crystallizes  best  from  a  slightly  acid 
solution. 

Zinc  sulphate  may  also  be  made  by  saturating  sulphuric  acid 
with  zinc  oxide  and  crystallizing. 

If  large  crystals  are  desired  let  the  saturated  solution  be  evap- 
orated slowly  at  the  ordinary  temperature  and  without  disturbing 
it. 

Description. — Colorless,  transparent  crystals ;  odorless ;  taste 
metallic,  astringent.  Soluble  in  0.6  part  of  water  at  15°,  and  in 
0.2  part  of  boiling  water ;  also  in  3  parts  of  glycerin.  Insoluble 
in  alcohol.  Reaction  acid. 

Re  crystallized  Zinc  Sulphate. 

White  vitriol    5  parts 

Water    3  parts 

Make  a  solution.  Acidify  it  with  i  part  of  diluted  sulphuric 
acid.  Boil  it  for  a  few  minutes.  Filter.  Conduct  a  current  of 
chlorine  into  the  warm  solution  until  it  acquires  the  odor  of  it. 
Add  a  small  quantity  of  iron-free  zinc  oxide  or  zinc  carbonate  to 
produce  a  slightly  turbid  mixture  containing  but  little  undissolved 
zinc  compound.  Digest  for, a  day  or  two,  shaking  occasionally. 
Bring  it  to  the  boiling  point.  Filter.  Acidify  again  with  diluted 
sulphuric  acid.  Crystallize  in  the  usual  way. 

Notes.  White  vitriol  contains  iron,  and  consists  of  an  opaque, 
granular,  more  or  less  dirty  salt  mass.  When  its  solution  is 


ZINC     SULPHATE.  63! 

strongly  acidified  and  boiled  it  can  be  filtered  quite  clear.  Chlorine 
converts  the  iron  present  into  ferric  sulphate.  The  iron  is  then 
easily  precipitated  by  digestion  with  zinc  oxide  or  zinc  carbonate 
in  slight  excess.  The  separation  of  the  iron  is  facilitated  by  boil- 
ing. After  filtration  the  solution  is  again  to  be  acidified  by  the 
addition  of  about  i  part  of  diluted  sulphuric  acid  because  the  salt 
crystallizes  most  satisfactorily  from  an  acid  solution. 

If  copper,  lead,  arsenic,  cadmium,  or  manganese  be  present, 
these  metals  are  removed  as  well  as  iron  by  this  method. 


ZINC    SULPHITE. 

ZINCI    SULPHIS. 

ZnSO3.2H2O=  179.3. 

Zinc   sulphate 60  parts 

Sodium    sulphite 53  parts 

Distilled  water,  sufficient. 

Dissolve  each  salt  separately  in  200  parts  of  cold  distilled 
water  and  filter  the  solutions.  Add  the  zinc  salt  solution  to  the 
solution  of  the  sodium  sulphite,  stirring  well.  A  precipitate  of 
zinc  sulphite  will  be  formed  in  the  course  of  from  twenty  to 
thirty  minutes. 

Decant  the  mother-liquor.  Wash  the  precipitate  with  a  limited 
amount  of  cold  water  until  the  washings  are  nearly  tasteless  and 
no  longer  contain  sodium  sulphate.  Dry  the  product  without 
the  aid  of  heat. 

Reaction.     ZnSO4+Na2SOs=ZnSO8+Na2SO4. 

Notes.  Cold  solutions  are  used  and  the  product  washed  and 
dried  at  the  ordinary  room  temperature  because  zinc  sulphite  is 
liable  to  be  decomposed  at  a  higher  temperature,  basic  salt  being 
formed. 

Description. — A  white,  crystalline  powder,  practically  insoluble 
in  water. 


632  ZINC     VALERATE. 

ZINC    VALERATE. 

ZINC    VALERIANAS. 

Zn(C5Hg02)2.2H20:=303.3. 

Sodium  valerate 25  parts 

Zinc   sulphate 29  parts 

Distilled  water,  sufficient. 

Dissolve  the  salts,  separately,  each  in  200  parts  of  water ;  heat 
the  solutions  to  boiling ;  mix  while  hot ;  let  the  mixture  cool.  Col- 
lect the  crystals,  wash  them  hastily  with  cold  water,  and  dry  them 
between  filter-paper. 

Another  crop  may  be  had  by  evaporating  the  mother  liquor  to 
20  parts,  cooling,  and  separating  the  crystals  formed. 

Reaction.     2NaC5H9O2+ZnSO4=Zn  ( C5H9O2)  2+Na2SO4. 

Notes.  As  the  zinc  valerate  is  lighter  than  the  solution  of  so- 
dium sulphate,  the  crystals  rise  to  the  surface  as  they  are  formed. 

The  salt  may  also  be  made  by  dissolving  3  parts  of  zinc  oxide 
in  a  mixture  of  5  parts  of  valeric  acid,  200  parts  of  alcohol,  and 
200  parts  of  water;  but  the  crystallization  is  tedious  on  account 
of  the  necessity  of  using  but  moderate  heat  in  evaporating  the 
solution. 

The  crystals  must  be  dried  without  the  aid  of  heat. 

Description. — Soft,  glistening  white  crystals,  soluble  in  about 
100  parts  of  water  and  in  40  parts  of  alcohol.  Taste  sweetish 
astringent,  finally  metallic. 


TABLES. 


TABLE    OF    ATOMIC    WEIGHTS. 


Aluminum  ... 

27 

Lead 

206  5 

Antimony 

120. 

Lithium 

7. 

Arsenic    

75. 

Magnesium 

24.2 

Barium  

137. 

Manganese                    .    . 

55. 

Bismuth  

208. 

Mercury  

200. 

Boron  

11. 

Nickel  

58.5 

Bromine  

80. 

Nitrogen  

14. 

Cadnium 

112 

Oxvsren 

16 

Calcium                                

40 

Phosphorus 

31 

Carbon     .    . 

12 

Platinum 

194 

Cerium              

139. 

Potassium  ... 

39. 

Chlorine  

35.4 

Silicon         ... 

28.3 

Chromium 

52 

Silver 

108 

Cobalt 

59 

Sodium 

23 

Copper              .  . 

63  5 

Strontium 

87.5 

Fluorine                   .  .    . 

19 

Sulphur       

32. 

Gold                        

197 

Tin      

119. 

Hydrogen               

1. 

Tungsten  

184. 

Iodine.                

126  5 

65.8 

In,n          

56. 

635 


Jp 

"" 

*! 

W 

<* 

us 

« 

^ 

cc 

r 

o 

I"1 

«1 

CO 

* 

Lft 

« 

s 

00 

Cfe 

O 
(N 

— 
(M 

Q. 

O 

cc 
O 

* 

tl 

r—  H 

0) 

* 

£ 

O 

oro 
sf 

0 

9* 
pf 

«: 

Q 

d5 

o" 

0 

a 

Q 

0 

& 

0 

0 
ffi 

5 

CO 

a 

0 

? 

0 

0 

O 

o 

lH 

TH 

I 

1 

1 

i 

0 
rH 

§ 

rH 

TH 

p 

o 
§ 

1 

1 

1C 

CO 

1 

1 

o 

TH 

1 

i 

| 

n 

to 

1C 

2 

r. 

05 

OJ 

CO 
05 

1C 

i- 

TH 

0 

rH 

§ 

rH 

1 

TH 

I 

1 

g 

l 

00 

TH 

CO 

fl 

I 

s? 

TH 

1 

TH 

CO 
1C 
rH 

CO 

05 

o 

00 

3 

CO 

TH 

0 

OS 

1 

OS 

S 

CO 

05 

rH 

0 

§ 

p 

i 

So 

0 

GO 

to 

CO 

3 

ol 

CO 

s 

1—  1 

rH 

rH 

IU 

on 

10 

J 

U 

^ 

8 

on 

£ 

in 

0 

cr 

CO 

CO 

CO 

CO 

01 
So 

o 

CO 

0 

or, 

*> 

^ 

OS 

TH 

?v 

05 

OS 
rH 

TH 

1C 

cs 

1C 

•* 

OS 

CO 

TH 

Tf 

CO 

O5 

•^ 

TH 

TH 

rH 

2 

O 

<* 

0 

2 

« 

1 

rH 

§ 

1 

1 

g 

I 

1 

s 

rH 

1 

1 

1 

1 

01 

TH 

05 

s 

i 

§ 

i 

s 

§ 

rH 

0 

0 

in 

Li. 
o 

us 

0 

s 

I 

1C 

1 

§ 

§ 

1C 

o 

10 

3 

T—  1 

1 

o 

1 

T—l 

rH 

CO 

O5 

1C 

GO 

§ 

8 

S 

CO 

{- 

I 
O 

* 

1 

TH 

0 

GO 
1C 

0 
CO 

00 

CO 
CO 

i 

1C 

0 
TH 

0 

05 

1C 
CO 

| 

to 

TH 

TH 

0 
05 

I 

i 

e 

s 

S 

u 

? 

05 

1C 

0 

CO 

05 

GO 

1C 

TH 

0 

CO 

CO 

£; 

3 

CO 

GO 

0 
00 

s 

0 
O? 

to 

o 

§ 

to 

rH 
10 

s 

CO 

rH 

M 

CO 

O5 

^ 

O5 

rH 

"^  . 

1C 

7-1 

O5 

1-1 

TH 

TH 

o 

° 

GO 

o 

< 

<N 

to 

O 

0 

rt 

§ 

« 

OO 

rH 

os 

00 

1C 

05 

CO 

i> 

CO 

0 

£ 

05 

TH 

CO 

CO 

CO 

S 

u 

h 

^ 

1C 

tu 

TH 

00 

o 

« 

1C 

t- 

CO 

CO 

T^ 

g 

oo 

O5 
00 

CO 

0 
CO 

00 

oo 

0 

CO 

CO 

to 

to 

1C 

1—  1 

00 

TH 

CO 
rH 

T—l 

O 

CO 

u 

i 

a 
h 

w 

be 

^ 

GB 

o3 

& 

0 

oro 

Q 

0 
K 
0 

q 

M5 
Q 

25 

p" 

q 

Q 

5 

0 

0 

£ 

0 

q 

l! 

90 

B 

TH 

(N 

50 

<* 

us 

» 

1- 

ao 

ct 

0 

rH 

<N 

CO 

-H 

^e 

^ 

*. 

X 

Ci 

0 

TH 

636 

<N     <N     <N 


f. 


O    I  T-     51     M 


<*>i»  o  3j5 15 


00 


S3 


CO     i 
TH      I 


0(0 


2 


i  S 


s 


§ 


§ 


5 


s 


be 


Ti 


^'^l?c  S18IS 


X 


f. 


*  3  8  SI 


o  [TH 


TABLE    OF   THERMOMETRIC    EQUIVALENTS. 

According  to  the  Centigrade  and  Fahrenheit  Scales. 


—40 

P.. 

1 

33.8 

47 

116.6 

C." 

F.« 

—40 

93 

199.4 

—39 

—38.2 

2 

35.6 

48 

118.4 

94 

201.2 

—38 

—36.4 

3 

37.4 

49 

120.2 

95 

203 

—37 

—34.6 

4 

39.2 

50 

122 

96 

204.8 

—36 

—32.8 

5 

41 

51 

123.8 

97 

206.6 

—35 

—31 

6 

42.8 

52 

125.6 

98 

208.4 

—34 

—29.2 

7 

44.6 

53 

127.4 

99 

210.2 

—33 

—27.4 

8 

46.4 

54 

129.2 

100 

212 

—32 

—25.6 

9 

48.2 

55 

131 

101 

213.8 

—31 

—23.8 

10 

50] 

56 

132.8 

102 

215.6 

—30 

—22 

11 

51.8 

57 

134.6 

103 

217.4 

—29 

—20.2 

12 

53.6 

58 

136.4 

104 

219.2 

—28 

—18.4 

13 

55.4 

59 

138.2 

105 

221 

—27 

—16.6 

14 

57.2 

60 

140 

110 

230 

—26 

—14.8 

15 

59 

61 

141.8 

115 

239 

—25 

—13 

16 

60.8 

62 

143.6 

120 

248 

—24 

—11.2 

17 

62.6 

63 

145.4 

125 

257 

—23 

—9.4 

18 

64.4 

64 

147.2 

130 

266 

—22 

—7.6 

19 

66.2 

65 

149 

135 

275 

—21 

—5.8 

20 

68 

66 

150.8 

140 

284 

—20 

—4 

21 

69.8 

67 

152.6 

145 

293 

—19 

—2.2 

22 

71.6 

68 

154.4 

150 

302 

—18 

—0.4 

23 

73.4 

69 

156.2 

155 

311 

—17 

1.4 

24 

75.2 

70 

158 

160 

320 

—16 

3.2 

25 

77 

71 

159.8 

165 

329 

—15 

5 

26 

78.8 

72 

161.6 

170 

338 

—14 

6.8 

27 

80.6 

73 

163.4 

175 

347 

—13 

8.6 

28 

82.4 

74 

165.2 

180 

856 

—12 

10.4 

29 

84.2 

75 

167 

185 

365 

—11 

12.2 

30 

86 

76 

168.8 

190 

374 

—10 

14 

31 

87.8 

77 

170.6 

195 

383 

-  9 

15.8 

32 

89.6 

78 

172.4 

200 

392 

—  8 

17.6 

33 

91.4 

79 

174.2 

210 

410 

—  7 

19.4 

84 

93.2 

80 

176 

220 

428 

—  6 

21.2 

35 

95 

81 

177.8 

230 

446 

—  5 

23 

36 

96.8 

82 

179.6 

240 

464 

—  4 

24.8 

37 

98.6 

83 

181.4 

250 

482 

—  3 

26.6 

38 

100.4 

84 

183.2 

260 

500 

—  2 

28.4 

39 

102.2 

85 

185  - 

270 

518 

—  1 

30.2 

40 

104 

86 

186.8 

280 

536 

—  0 

32 

41 

105.8 

87 

188.6 

290 

554 

42 

107.6 

88 

190.4 

300 

572 

43 

109.4 

89 

192.2 

310 

590 

44 

111.2 

90 

194 

320 

608 

45 

113 

91 

195.8 

330 

626 

46 

114.8 

92 

197.6 

638 


ACETIC    ACID. 

According  to  Oudemans. 


Percent 
of 
absolute 
Acetic 
Acid. 

Specific  Gravity 
at  15°  C. 

Percent 
of 
absolute 
Acetic 
Acid. 

Specific  Gravity 
at  15°  C. 

Percent 
-    of 
absolute 
Acetic 
Acid. 

Specific  Gravity 
at  15°  C. 

1 

1.0007 

34 

1.0459 

67 

1.0721 

2 

1.0022 

35 

1.0470 

68 

1.0725 

3 

1.0037 

36 

1.0481 

69 

1.0729 

4 

1.0052 

37 

1.0492 

70 

1.0733 

5 

1.0067 

38 

1.0502 

71 

1.0737     . 

6 

1.0083 

39 

1.0513 

72 

1.0740 

7 

1.0098 

40 

1.0523 

73 

1.0742 

8 

1.0113 

41 

1.0533 

74 

1.0744 

9 

1.0127 

42 

1.0543 

75 

1.0746 

10 

1.0142 

43 

1.0552 

76 

1.0747 

11 

1.0157 

44 

1.0562 

77 

1.0748 

12 

1.0171 

45 

1.0571 

78 

1.0748 

13 

1.0185 

46 

1.0580 

79 

1.0748 

14 

1.0200 

47 

1.0589 

80 

1.0748 

15 

1.0214 

48 

1.0598 

81 

1.0747 

16 

1.0228 

49 

1.0607 

82 

.0746 

17 

1.0242 

50 

1.0615 

83 

.0744 

18 

1.0256 

51 

1.0623 

84 

.0742 

19 

1.0270 

52 

1.0631 

85 

.0739 

20 

1.0284 

53 

1.0638 

86 

.0736 

21 

1.0298 

54 

1.0646 

87 

.0731 

22 

1.0311 

55 

1.0653 

88 

.0726 

23 

1.0324 

56 

1.0660 

89 

.0720 

24 

1.0337 

57 

1.0666 

90 

.0713 

25 

1.0350 

58 

1.0673 

91 

.0705 

.26 

1.0363 

59 

1.0679 

92 

.0696 

27 

1.0375 

60 

1.0685 

93 

.0686 

28 

1.0388 

61 

1.0691 

94 

.0674 

29 

1.0400 

62 

1.0697 

95 

.0660 

30 

1.0412 

63 

1.0702 

96 

.0644 

31 

1.0424 

64 

1.0707 

97 

.0625 

32 

1.0436 

65 

1.0712 

98 

.0604 

33 

1.0447 

66 

1.0717 

99 

.0580 

639 


HYDROBROMIC   ACID. 

According  to  Biel. 


Percent 
Br. 

Specific 
Gravity 
at  15°  C. 

Percent 
HBr. 

Specific 
Gravity 
at  15°  C. 

Percent 
HBr. 

Specific 
Gravity 
at  15°  C. 

Percent 
HBr. 

Specific 
Gravity 
at  15°  C. 

1 

1.0082 

14 

1.110 

27 

1.229 

40 

1.375 

2 

1.0155 

15 

1.119 

28 

1.239 

41 

1.388 

3 

1.0230 

16 

1.127 

29 

1.249 

42 

1.401 

4 

1.0305 

17 

1.136 

30 

1.260 

43 

1.415 

5 

1.038 

18 

1.145 

31 

1.270 

44 

1.429 

6 

1.046 

19 

1.154 

32 

1.281 

45 

1.444 

7 

1.053 

20 

1.163 

33 

1.292 

46 

1.459 

8 

1.061 

21 

1.172 

34 

1.303 

47 

1.474 

9 

1.069 

22 

1.181 

35 

1.314 

48 

1.490 

10 

1.077 

23 

1.190 

36 

1.326 

49 

1.496 

11 

1.085 

24 

1.200 

37 

1.338 

50 

1.513 

12 

1.093 

25 

1.209 

38 

1.350 

13 

1.102 

26 

1.219 

39 

1.362 

HYDROCHLORIC    ACID. 

According  to  G.  Lunge  and  L.  Marchlewski. 


Specific  Gravity 
at  15° 
(H20  at  40=1.) 

Per  Cent,  of 
HC1. 

Grams  of 
HClin 
1  Liter. 

Specific  Gravity 
at  15° 
(H2Oat  40=1.) 

PerCent.  of 
HC1. 

Grams  of 
HClin 
1  Liter. 

1.000 

0.16 

1.6 

1.100 

20.01 

220 

1.005 

1.15 

12 

1.105 

20.97 

232 

1.010 

2.14 

22 

1.110 

21.92 

243 

1.015 

3.12 

32   ' 

1.115 

22.86 

255 

1.020 

4.13 

42 

1.120 

23.82 

267 

1.025 

5.15 

53 

1.125 

24.78 

278 

1.030 

6.15 

64 

1.130 

25.75 

291 

1.035 

7.15 

74 

1.135 

26.70 

303 

1.040 

8.16 

85 

1.140 

27.66 

315 

1.045 

9.16 

96 

1.145 

28.61 

328 

1.050 

10.17 

107 

1.150 

29.57 

340 

1.055 

11.18 

118 

1.155 

30.55 

353 

1.060 

12.19 

129 

1.160 

31.52 

366 

1.065 

13.19 

141 

1.165 

32.49 

379 

1.070 

14.17 

152 

1.170 

33.46 

392 

1.075 

15.16 

163 

1.175 

34.42 

404 

1.080 

16.15 

174 

1.180 

35.39 

418 

1.085 

17.13 

186 

1.185 

36.31 

430 

1.090 

18.11 

197 

1.190 

37.23 

443 

1.095 

19.06 

209 

1.195 

38.16 

456 

1.200 

39.11 

469 

640 


NITRIC    ACID. 

According  to  G.  Lunge  and  H.  Rey. 


Specific  Gravity 
at  15° 
(H2O  at  4°=1.) 

Per  Cent,  of 
HN03. 

Grams 
of  HN03 
in  1  Liter. 

Specific  Gravity 
at  15° 
(H20  at  4°-l.) 

Per  Cent,  of 
HN03. 

Grams 
of  HNO3 
in  1  Later. 

.000 

0.10 

1 

1.255 

40.58 

509 

.005 

1.00 

10 

1.260 

41.34 

521 

.010 

1.90 

19 

1.265 

42.10 

533 

.015 

2.80 

28 

1.270 

42.87 

544 

.020 

3.70 

38 

1.275 

43.64 

556 

1.025 

4.60 

47 

1.280 

44.41 

568 

1.030 

5.50 

57 

1.285 

45.18 

581 

1.035 

6.38 

66 

1.290 

45.95 

593 

1.040 

7.26 

75 

1.295 

46.72 

608 

1.045 

8.13 

85 

1.300 

47.49 

617 

1.050 

8.99 

94 

1.305 

48.26 

630 

1.055 

9.84 

104 

1.310 

49.07 

643 

1.060 

10.68 

113 

1.315 

49.89 

656 

1.065 

11.51 

123 

1.320 

50.71 

669 

1.070 

12.33 

132 

1.325 

51.53 

683 

1.075 

13.15 

141 

1.330 

52.37 

697 

1.080 

13.95 

151 

1.335 

53.22 

710 

1.085 

14.74 

160 

1.340 

54.07 

725 

1.090 

15.53 

169 

1.345 

54.93 

739 

1.095 

16.32 

179 

1.350 

55.79 

758 

1.100 

17.11 

188 

1.355 

56.66 

768 

1.105 

17.89 

198 

1.360 

57.57 

783 

1.110 

18.69 

207 

1.365 

58.48 

798 

1.115 

19.45 

817 

1.370 

59.39 

814 

1.120 

20.23 

227 

1.375 

60.30 

829 

1.125 

21.00 

236 

1.380 

61.27 

846 

1.130 

21.77 

246 

1.385 

62.24 

862 

1.135 

22.54 

256 

1.390 

63.23 

879 

1.140 

23.31 

266 

1.395 

64.25 

896 

1.145 

24.08 

276 

1.400 

65.30 

914 

1.150 

24.84 

286 

.405 

66.40 

933 

1.155 

25.60 

296 

.410 

67.50 

952 

1.160 

26.36 

306 

.415 

68.63 

971 

1.165 

27.12 

316 

.420 

69.80 

991 

1.170 

27.88 

326 

.425 

70.98 

1011 

1.175 

28.63 

336 

.430 

72.17 

1032 

.180 

29.38 

347 

.435 

73.39 

1053 

.185 

30.13 

357 

.440 

74.68 

1075 

.190 

30.88 

367 

.445 

75.98 

1098 

.195 

31.62 

378 

.450 

77.28 

1121 

.200 

32.36 

388 

.455 

78.60 

1144 

.205 

33.09 

399 

.460 

79.98 

1168 

.210 

33.82 

409 

1.465 

81.42 

1193 

.215 

34.55 

420 

1.470 

82.90 

1219 

1.220 

35.28 

430 

1.475 

84.45 

1246 

1.225 

36.03 

441 

1.480 

86.05 

1274 

1.230 

36.78 

452 

1.485 

87.70 

1802 

1.235 

3T.53 

463 

1.490 

89.60 

1335 

1.240 

38.29 

475 

1.495 

91.60 

1369 

1.245 

39.05 

486 

1.500 

94  09 

1411 

1.250 

39.82 

498 

1.501 

94.60 

-ssz.  

1420 

641 


NITRIC    ACID-Continued. 


Specific  Gravity 
at  15° 
(H2Oat4°=l) 

Per  Cent,  of 
HN03. 

Grams 
of  HN03 
in  1  Liter. 

Specific  Gravity 
at  15° 
(H2OaU°  =  l.) 

Per  Cent,  of 
HN03. 

Grams 
of  HNO, 

in  1  Liter-. 

1.502 

95.08 

1428 

1.512 

98.53 

1490 

1.503 

95.55 

1436 

1.513 

98.73 

1494 

1.504 

96.00 

1444 

1.514 

98.90 

1497 

1.505 

96.39 

1451 

1.515 

99.07 

1501 

1.506 

96.76 

1457 

1.516 

99.21 

1504 

1.507 

97.13 

1464 

1.517 

99.34 

1507 

1.508 

97.50 

1470 

1.518 

99.46 

1510 

1.509 

97.84 

1476 

1.519 

99.57 

1512 

1.510 

98.10 

1480 

1.520 

99.67 

1515 

1.511 

98.32 

1486 

PHOSPHORIC    ACID. 

According  to   A,   B.   Lyons.* 


Specific  Gravity 
at  15° 
(H2O  at  4°=1.) 

Percentage  of 
H3P04. 

Specific  Gravity 
at  15° 
(H2Oatl5°=l.) 

Percentage  of 
H3P04. 

Specific  Gravity 
at  15° 
(H20  at  40=1.) 

Percentage  of 
H,P04. 

1.0000 

0 

1.1816 

29 

1.4215 

58 

1.0056 

1 

1.1889 

30 

1.4312 

59 

.0113 

2 

1.1962 

31 

-      1.4409 

60 

.0170 

3 

1.2035 

32 

1.4508 

61 

.0226 

4 

1.2110 

33 

1.4607 

62 

.0283 

5 

1.2184 

34 

1.4706 

63 

.0340 

6 

1.2260 

35 

1.4807 

64 

.0398 

7 

1.2336 

36 

1.4908 

65 

.0457 

8 

1.2412 

37 

1.5010 

66 

.0517 

9 

1.2489 

38 

1.5113 

67 

.0577 

10 

1.2567 

39 

1.5216 

68 

.0637 

11 

1.2645 

40 

1.5321 

69 

.0698 

12 

1.2724 

41 

1.5426 

70 

.0759 

13 

1.2804 

42 

1.5532 

71 

.0821 

14 

1.2885 

43 

1.5638 

72 

.0882 

15 

1.2967 

44 

1.5746 

73 

.0945 

16 

1.3050 

45 

1.5854 

74 

.1008 

17 

1.3134 

46 

1.5963 

75 

.1072 

18 

1.3219 

47 

1.6073 

76 

.1136 

19 

1.3304 

48 

1.6193 

77 

.1201 

20 

1.3391 

49 

1.6304 

78 

.1266 

21 

1.3479 

50 

1.6416 

79 

.1332 

22 

1.3568 

51 

1.6529 

80 

.1399 

23 

1.3657 

52 

1.6642 

81 

1.1467 

24 

1.3748 

53 

1.6756 

82 

1.1535 

25 

1.3840 

54 

1.6871 

83 

1.1604 

26 

1.3932 

55 

1.6986 

84 

1.1674 

27 

1.4026 

56 

1.7102 

85 

1.1745 

28 

1.4120 

57 

*  From  the  Pharmacopoeia  of  the  United  States. 

642 


SULPHURIC    ACID. 

According:  to  G.  Lunge  and  M.  Isler. 


Specific  Gravity 
at  16° 
(HaO  at  4°-l.) 

Percent 
of  H3S04. 

Grams 
of  H2SO4 
in  1  Liter. 

Specific  Gravity 
at  15° 
(H20at4°-l.) 

Percent 
of  H2S04. 

Grams 
of  H,S04 
in  1  Liter. 

1.000 

0.09 

1 

1.260 

34.57 

435 

1.005 

0.83 

8 

1.265 

35.14 

444 

1.010 

1.57 

16 

1.270 

35.70 

454 

.015 

2.30 

23 

1.275 

36.29 

462 

.020 

8.03 

81 

1.280 

36.87 

472 

.025 

3.76 

39 

1.285 

37.45 

481 

.030 

4.49 

46 

1.290 

38.03 

490 

.035 

5.23 

54 

1.295 

38.61 

500 

.040 

5.96 

62 

1.300 

39.19 

510 

.045 

6.67 

71 

1.805 

39.77 

519 

.050 

7.  87 

77 

1.310 

40.35 

529 

1.055 

8.07 

85 

1.315 

40.93 

538 

1.060 

8.77 

93 

1.320 

41.50 

548 

1.065 

9.47 

102 

1.325 

42.08 

557 

1.070 

10.19 

109 

1.330 

42.66 

567 

1.075 

10.90 

117 

1.335 

43.20 

577 

1.080 

11.60 

125 

.340 

43.74 

586 

1.085 

12.30 

133 

.345 

44.28 

596 

1.090 

12.99 

142 

.350 

44.82 

605 

1.095 

13.67 

150 

.355 

45.35 

614 

.100 

14.85 

158 

.360 

45.88 

624 

.105 

15.03 

166 

.365 

46.61 

633 

.110 

15.71 

175 

.370 

46.94 

643 

.115 

16.36 

183 

.375 

47.47 

653 

.120 

17.01 

191 

.380 

48.00 

662 

.125 

17.66 

199 

.385 

48.53 

672 

.130 

18.31 

207 

.390 

49.06 

682 

.135 

18.96 

215 

.395 

49.59 

692 

.140 

19.61 

223 

.400 

50.11 

702 

.145 

20.26 

231 

.405 

50.63 

711 

.150 

20.91 

239 

1.410 

51.15 

721 

.155 

21  55 

248 

1.415 

51.66 

780 

.160 

22.19 

257 

1.420 

52.15 

740 

.165 

22.83 

266 

1.425 

52.63 

750 

.170 

23.47 

275 

1.430 

53.11 

759 

.175 

24.12 

283 

1.435 

53.59 

769 

.180 

24.76 

292 

1.440 

54.07 

779 

.185 

25.40 

301 

1  445 

54.55 

789 

.190 

26.04 

310 

1.450 

55.03 

798 

.195 

26.68 

319 

1.455 

55.50 

808 

.200 

27.32 

328 

1.460 

55.97 

817 

.205 

27.95 

337 

1.465 

56.43 

827 

.210 

28.58 

346 

1  470 

56.90 

837 

.215 

29.21 

355 

1.475 

57.37 

846 

.220 

29.84 

364 

1.480 

57.83 

856 

.225 

30.48 

373 

1.485 

58.28 

865 

.230 

31.11 

382 

1.490 

58.74 

876 

.235 

31.70 

391 

.495 

59.22 

885 

.240 

32.28 

400 

.500 

59.70 

896 

.245 

32.86 

409 

.505 

60.18 

906 

.250 

33.43 

418 

.510 

60.65 

916 

.255 

34.00 

426 

.515 

61.12 

926 

643 


SULPHURIC    ACID.-Continued. 


Specific  Gravity 
at  15° 
(H2O  at  4°=i.) 

Percent 
of  H2S04. 

Grams 
of  H2SO4 
in  1  Liter. 

Specific  Gravity 
at  15° 
(H2O  at  4°=1.) 

Percent 
of  H2S04. 

Grams 
of  H2S04 
in  1  Liter. 

1.520 

61.59 

936 

1.745 

81.12 

1416 

1.525 

62.06 

946 

1.750 

81.56 

1427 

1.530 

62.53 

957 

1.755 

82.00 

1439 

1.535 

63.00 

967 

1.760 

82.44 

1451 

1.540 

63.43 

977 

1.765 

82.88 

1463 

1.545 

63.85 

987 

1.770 

83.32 

1475 

1.550 

64.26 

996 

1.775 

83.90 

1489 

1.555 

64.67 

1006 

1.780 

84.50 

1504 

1.560 

65.01 

1015 

1.785 

85.10 

1519 

1.565 

65.49 

1025 

1.790 

85.70 

1534 

1.570 

65.90 

1035 

1.795 

86.30 

1549 

1.575 

66.30 

1044 

1.800 

86.90 

1564 

1.580 

66.71 

1054 

1.805 

87.60 

1581 

1.585 

67.13 

1064 

1.810 

88.30 

1598 

1.590 

67.59 

1075 

1.815 

89.05 

1621 

1.595 

68.05 

1085 

1.820 

90.05 

1639 

1.600 

68.51 

1096 

.821 

90.20 

1643 

1.605 

68.97 

1107 

.822 

90.40 

1647 

1.610 

69.43 

1118 

.823 

90.60 

1651 

.615 

69.89 

1128 

.824 

90.80 

1656 

.620 

70.32 

1139 

.825 

91.00 

1661 

.625 

70.74 

1150 

.826 

91.25 

1666 

.630 

71.16 

1160 

.827 

91.50 

1671 

.635 

71.57 

1170 

.828 

91.70 

1676 

.640 

71.99 

1181 

1.829 

91.90 

1681 

.645 

72.40 

1192 

1.830 

92.10 

1685 

.650 

72.82 

1202 

1.831 

92.30 

1690 

.655 

73.23 

1212 

1.832 

92.52 

1695 

.660 

73.64 

1222 

1.833 

92.75 

1700 

.665 

74.07 

1233 

1.834 

93.05 

1706 

.670 

74.51 

1244 

1.835 

93.43 

1713 

.675 

74.97 

1256 

1.836 

93.80 

1722 

.680 

75.42 

1267 

1.837 

94.20 

1730 

.685 

75.86 

1278 

1.838 

94.60 

1739 

1.690 

76.30 

1289 

1.839 

95.00 

1748 

1.695 

76.73 

1301 

1.840 

95.60 

1759 

1.700 

77.17 

1312 

1.8405 

95.95 

1765 

1.705 

77.60 

1323 

1.8410 

97.00 

1786 

1.710 

78.04 

1334 

1.8415 

97.70 

1799 

1.715 

78.48 

1346 

1.8410 

98.20 

1808 

1.720 

78.92 

1357 

1.8405 

98.70 

1816 

1.725 

79.36 

1369 

1.8400 

99.20 

1825 

1.730 

79.80 

1381 

1.8395 

99.45 

1830 

1.735 

80.24 

1392 

1.8390 

99.70 

1834 

1.740 

80.68 

1404 

1.8385 

99.95 

1838 

644 


AMMONIA    SOLUTION. 
According  to  G.  Lunge  and  T.  Wiernlk. 


Specific  Gravity 
at  15° 
(HaOat  40-1.) 

Percent, 
of 
H3N. 

Grams  of 
H3Nin 
1  Liter. 

Specific  Gravity 
at  15° 
(HjO  at4°-=l.) 

Percent, 
of 
H3N. 

Grams  of 
H3Nin 
1  Liter. 

1.000 

0.00 

0.0 

0.940 

15.63 

146.9 

0.998 

0.45 

4.5 

0.938 

16.22 

152.1 

0.996 

0.91 

9.1 

0.936 

16.82 

157.4 

0.994 

1.37 

13.6 

0.934 

17.42 

162.7 

0.992 

1.84 

18.2 

0.932 

18.03 

168.1 

0.990 

2.31 

22.9 

0.930 

18.64 

173.4 

0.988 

2.80 

27.7 

0.928 

19.25 

178.6 

0.986 

3.30 

32.5 

0.926 

19.87 

184.2 

0.984 

3.80 

37.4 

0.924 

20.49 

189.3 

0.982 

4.30 

42.2 

0.922 

21.12 

194.7 

0.980 

4.80 

47.0 

0.920 

21.75 

200.1 

0.978 

5.30 

51.8 

0.918 

22.39 

205.6 

0.976 

5.80 

56.6 

0.916 

23.03 

210.9 

0.974 

6.30 

61.4 

0.914 

23.68 

216.3 

0.972 

6.80 

66.1 

0.912 

24.33 

221.9 

0.970 

7.31 

70.9 

0.910 

24.99 

227.4 

0.968 

7.82 

75.7 

0.908 

25.65 

232.9 

0.966 

8.33 

80.5 

0.906 

26.31 

238.3 

0.964 

8.84 

85.2 

0.904 

26.98 

243.9 

0.962 

9.35 

89.9 

0.902 

27.65 

249.4 

0.960 

9.91 

95.1 

0.900 

28.33 

255.0 

0.958 

10.47 

100.3 

0.898 

29.01 

260.5 

0.956 

11.03 

105.4 

0.896 

29.69 

266.0 

0.954 

11.60 

110.7 

0.894 

30.37 

271.5 

0.952 

12.17 

115.9 

0.892 

31.05 

277.0 

0.950 

12.74 

121.0 

0.890 

31.75 

282.6 

0.948 

13.31 

126.2 

0.888 

32.50 

288.6 

0.946 

13.88 

131.3 

0.886 

33.25 

294.6 

0.944 

14.46 

136.5 

0.884 

34.10 

301.4 

0.942 

15.04 

141.7 

0.882 

34.95 

308.3 

645 


SOLUTION    OF    POTASSIUM    HYDROXIDE. 

According  to  Gerlach. 


Specific  Gravity 

Percent 

Specific  Gravity 

Percent 

Specific  Gravity 

Percent 

at  15°  C. 

of  KOH. 

at  15°  C. 

of  KOH. 

at  15°  C. 

of  KOH. 

1.009 

1 

1.230 

25 

1.527 

49 

1.017 

2 

1.241 

26 

1.539 

50 

1.025 

3 

1.252 

27 

1.552 

51 

1.033 

4 

1.264 

28 

1.565 

52 

1.041 

5 

1.278 

29 

1.578 

53 

1.049 

6 

1.288 

30 

1.590 

54 

.058 

7 

1.300 

31 

1.604 

55 

.065 

8 

1.311 

32 

1.618 

56 

.074 

9 

1.324 

33 

1.630 

57 

.083 

10 

.336 

34 

1.641 

58 

.092 

11 

.349 

35 

1.655 

59 

.101 

12 

.361 

36 

1.667 

60 

.111 

13 

.374 

37 

1.682 

61 

.119 

14 

.387 

38 

1.695 

62 

.128 

15 

.400 

39 

1.705 

63 

.137 

16 

.411 

40 

1.718 

64 

.146 

17 

.425 

41 

1.729 

65 

1.155 

18 

.438 

42 

1.740 

66 

1.166 

19 

.450 

43 

1.751 

67 

1.177 

20 

.462 

44 

1.768 

68 

1.188 

21 

.475 

45 

1.780 

69 

1.198 

22 

.488 

46 

1.790 

70 

1.209 

23 

1.499 

47 

1.220 

24 

1.511 

48 

SOLUTION    OF    SODIUM    HYDROXIDE. 

According  to  Gerlach. 


Specific  Gravity 
at  15°  C. 

Percent 
of  NaOH. 

Specific  Gravity 
at  15°  C. 

Percent 
of  NaOH. 

Specific  Gravity 
at  15°  C. 

Percent 
of  NaOH. 

1.012 

1 

1.279 

25 

1.529 

49 

1.023 

2 

1.290 

26 

1.540 

50 

.035 

3 

1.300 

27 

.550 

51 

.046 

4 

1.310 

28 

.560 

52 

.059 

5 

1.321 

29 

.570 

53 

.070 

6 

1.332 

30 

.580 

54 

.081 

7 

1.343 

31 

.591 

55 

1.092 

8 

1.353 

32 

.601 

56 

1.103 

9 

1.363 

33 

.611 

57 

1.115 

10 

1.374 

34 

.622 

58 

1.126 

11 

1.384 

35 

.633 

59 

1.137 

12 

1.395 

36 

.643 

60 

1.148 

13 

1.405 

37 

.654 

61 

1.159 

14 

1.415 

38 

.664 

62 

1.170 

15 

1.426 

39 

.674 

63 

1.181 

16 

1.437 

40 

.684 

64 

1.192 

17 

1.447 

41 

.695 

65 

1.202 

18 

1.456 

42 

.705 

66 

1.218 

19 

1.468 

43 

.715 

67 

1.225 

20 

1.478 

44 

.726 

68 

1.236 

21 

1.488 

45 

.737 

69 

1.247 

22 

1.499 

46 

.748 

70 

1.258 

23 

1.508 

47 

1.269 

24 

1.519 

48 

646 


INDEX 


TO   THE   SECOND  VOLUME. 


Actetate,  aluminum,  256. 

ammonium,  solution,  266. 

barium,  292. 

calcium,  317. 

chromium,  342. 

copper,  347-348. 

ferric,  solution,  368-370. 

ferric,  tincture,  371. 

lead,  448-451. 

magnesium,  468. 

potassium,  524. 

sodium,  572-574. 

zinc,  619-620. 

Acetates,    solubilities,    148,    149-150. 
Acid,  acetic,  216-218. 

acetic  as  a  solvent,  32,  33. 

acetic,  table,  639. 

arsenous,  290. 

benzoic,  218-220. 

boric,  220-222. 

chloroplatinic,  523. 

chromic,  344. 

citric,  222-224. 

hydriodic,  224. 
-hydrobromic,  225-226. 

hydrobromic,  table,  640. 

hydrochloric,  226-228. 

hydrochloric,  table,  640. 

hydrocyanic,  228-231. 

hypophosphorous,  231-232. 

lactic,  232. 

metaphosphoric,  243. 

nitric,  233-235. 

nitric,  in  oxidation,   124. 

nitric,  table,  641-642. 

nitrohydrochloric,   235-236. 

oleic,  236. 

oxalic,  237-238. 

phosphoric,  238-243. 

phosphoric^  table,  642. 

salicylic,  243-245. 

sulphuric,  245-248. 

sulphuric,  aromatic,  248. 

sulphuric,  table,  643-644. 

sulphurous,  248-250. 

tartaric,  251. 

valeric,  252. 
Acids,  action  on  carbonates,  ui. 


647 


Acids,  action  on  hydroxides. 

action  on  metals,  120. 

action  on  nitrites,  121. 

action  on  oxides,  121. 

action  of  sulphides,   121. 

action  on  sulphites,   121. 

care  in  handling,  197-200. 

notes  on,  215. 

organic,   solubility  of,   149. 

strength  of,  8-10. 

sulphuric,  29-30. 
Aethiops  mineralis,  510. 
Air,  damaging  effects  of,  138-140. 
Albuminate,   iron,  372-374. 
Alcohol  as  a  solvent,  33,  149,   150. 
Alcohol  lamps,  149-150,  187-188. 
Alkali  solutions,  strength,  8. 
Alkalies,  destructive  action  of,  200. 
Allanite,  337. 
Alum,  253-256. 

chromic,  343. 

iron,  445-446. 
Aluminated  copper,  355. 
Aluminum  compounds,  253-263. 
Aluminum  compounds,  solubilities, 

143- 
Ammonia  water,  263-265. 

water,  table,  645. 

Ammoniacal   copper  sulphate,  354. 
Ammoniated  copper,  353. 

mercury,  492. 
Ammonium  compounds,  263-280. 

compounds,   solubilities,    142. 
Amorphous  substances,  78,  101. 
Antidote  for  arsenic,  413. 
Antimonate,  potassium,  525. 
Antimony  compounds,  280-290. 

compounds,  solubility,  145. 
Apparatus  fittings,  74. 

outfit,  195. 

stands,  76,  77. 

Aqueous  fusion,  18,  19,  87,   133. 
Archimedes,  law  of,  153. 
Argols,  528. 
Arsenate,  iron.  374. 

sodium,  574. 

sodium,  solution,  575. 
Arsenates,  solubilities,  150. 


648 


INDEX. 


Arsenic    compounds,    290-292,    374, 

526,  574,  575- 
compounds,     solubilities,     145, 

150. 

Arsenite,  potassium,  526. 
Atomic   weights,    tables,    635,   635- 

637. 
Balances,   181-182. 

hydrostatic,  155,  157. 
Barium  compounds,  292-298. 

compounds,  solubilities,  142. 
Basham's  mixture,  371. 
Baths,  189-191. 
Beakers,   no. 
Bellows,    184. 
Benzoate,  ammonium,  268. 

bismuth,  299. 

calcium,  318. 

ferric,  375. 

lithium,  464. 

mercuric,  488. 

potassium,  527. 

sodium,  575. 

Benzoates,  solubilities,  148, 149, 150. 
Bicarbonate,  ammonium,  269. 

potassium,  527. 

sodium,  576-577. 
Bismuth,  298. 
Bismuth  compounds,  299-314. 

compounds  solubilities,  145. 
Bisulphide,  carbon,  337. 
Bisulphite,   sodium,   578. 
Bitartrate,   potassium,  528. 

sodium,  578. 
Bleaching  powder,  342. 
Blower,  184. 
Blue-stone,  352. 
Boiling  points,  63,  72. 
Boiling  vessels,  66. 
Bone  phosphate,  328. 
Borate,  sodium,  606. 
Borates,  solubilities,  147. 
Borax,  606. 
Borax-tartar,  529. 
Borocitrate,  magnesium,  469. 

potassium,  539. 
Boroglycerin,  221. 
Borotartrate,  potassium,  530. 

potassium-sodium,  529. 
Bromate,  potassium,  530. 
Bromide,  ammonium,  270-271. 

barium,  293. 

calcium,  318. 

ferrous,  375. 

lithium,  465. 

mercuric,  489. 

potassium,  531-533- 

sodium,  578-579. 

strontium,  609. 

zinc,  621. 


Bromides,  solubilities,  146,  149. 
Bromine,  200-202,  314,  315. 
Buchner  funnel,  47. 
Burner,  Erlenmeyer,  185. 
Burners,  183-186,  188. 
Burner  supports,  189. 
Buoyancy,  153,  154. 
Cadmium  compounds,  315-317. 

compounds,   solubilities,    143. 
Calcination,  21. 
Calcium  compounds,  317-334. 

compounds,     solubilities,     142- 

143. 
Calomel,  510-514. 

precipitated,  510-514. 
Calx,  327. 

sulphurata,  332. 
Carbon,  334. 

dioxide,  125,  335. 

disulphide,  337. 
Carbamate,  ammonium,  272. 
Carbonate,  ammonium,  272. 

barium,  293. 

cadmium,  315. 

calcium,  319. 

bismuthyl,  306-308. 

iron,  mass,  378. 

iron,  saccharated,  376. 

lead,  451. 

lithium,  465. 

magnesium,  469-470. 

manganese,  482. 

potassium,  533-535- 

sodium,  579-582. 

strontium,  609. 

zinc,  621-622. 
Carbonates,  action  on  acids,  121. 

solubilities,  147,   150. 
Carbonic  acid  gas,  335. 

acid  water,  335. 
Carlsbad  salt,  604,  605. 
Casseroles,  50. 
Centrifugator,  96. 
Cerite,  337. 
Cerium  compounds,  337-338. 

compounds,  solubilities,  143. 
Chalk,  prepared,  320. 
Charcoal,  animal,  334. 
Chemical  solution,  37,  117-118,  121, 

123,  124. 

Chloramide,  mercuric,  493. 
Chlorate,  potassium',  535. 

sodium,  582. 

Chlorates,  solubility,  146,   149,   150. 
Chloride,  aluminum,  257-258. 

ammonium,  274-276. 

antimony,  280-281. 

barium,  294. 

bismuthyl,  312. 

cadmium,  316. 


INDEX. 


649 


Chloride,  calcium,  320. 

copper,  349. 

ferric,  379-382. 

ferric,  solution,  382-387. 

ferric,  tincture,  387-390. 

ferrous,  390. 

gold,  356. 

gold  and  sodium,  357-358. 

lithium,  465. 

magnesium,  471-472. 

manganese,  484. 

mercuric,  489-491. 

mercurous,  510-514. 

of  lime,  342. 

potassium,  537. 

silver,  566. 

sodium,  583-584. 

strontium,    610. 

tin,  619. 

zinc,  622. 
Chlorides,  solubility,  145,   146,  149, 

150. 
Chlorine,  125,  338-341. 

water,  339--34O. 
Chlorinated  lime,  342. 
Chloroplatinic  acid,  523. 
Chromate,  barium,  296. 

lead,  452. 

potassium,  544. 
Chrome  alum,  343. 
"Chromic  acid,"  344,  346. 

anhydride,  344. 
Chromium  compounds,  342-346. 

compounds,   solubilities,   144. 
Circulatory  displacement,  37. 
Citrate,  ammonium,  268. 

bismuth,  300. 

ferric,  391-393- 

ferric  solution,  393-396. 

ferric,  with  quinine,  396-400. 

ferric,  with  strychnine,  400. 

lithium,  466. 

magnesium,  472-475. 

potassium,  538. 

sodium,  solution,  584. 
Citrates,  solubilities,  148,   150. 
Citrine  ointment,  499. 
Clarification  of  liquids,  47-62. 
Cobalt  compounds,   solubility,   143. 
Co-efficients  of  solubility,  44. 
Colloids,  98. 

Combustion  of  metals,  21. 
Compounds,  true  chemical,  29. 
Condensers,  73-76. 
Condensing-watcr,  71-72. 
Copper  compounds,  347-354- 

compounds,  solubility,  144. 
Cork  borer,  75. 
Corrosive  sublimate,  489-491. 
Cream  of  tartar,  528. 


Crucibles,   17,  18. 
Crystal  meal,  78. 

water,   18-20,  85-87. 
Crystallization,  78-97. 
Crystallizers,  92,  96. 
Crystallography,   81-84. 
Crystalloids,  98. 
Cubes,  81,  85. 
Cyanate,  potassium,  540. 
Cyanide,   mercury,   493-496. 

potassium,  541. 

silver,  567. 

zinc,   624. 

Cyanides,  solubilities,  146,  149. 
Decantation,  48-50,  109,  in. 

jar,   109. 

Decrepitation,  85. 
Dehydration,  18,  19. 
Deliquescence,  29,  96,  130,  134,  140. 
Densities  of  solids  and  liquids,  151- 

166. 

Dermatol,  308. 
Desiccation,  18,  19,  96. 
Desiccators,  96. 
Diachylon  plaster,  459. 
Dialysed  iron,  99,  403. 
Dialyser,  98. 
Dialysis,  98-99. 
Dichromate,  potassium,  542. 
Dioxide,  barium,  296. 

hydrogen,  359-363. 
Dissociation   of  salts   in   solutions, 

28-32. 

Distillation,  70-77. 
Disulphide,  carbon,  337. 
Donovan's  solution,  291. 
Drum  sieve,  14. 
Dry  oxidation,  21. 
Dry  processes,  4. 
Drying  closets,  19,  179. 
Efflorescence,   19,  87,  96,   130. 
Elixirs,   129. 
Elutriation,  13. 
Epsom  salt,  480. 
Erlenmeyer  flasks,   no. 
Ethylate,  sodium,  586. 
Ethylsulphate,  sodium,  585. 
Evaporation,  63-69. 

dishes,  67. 
Exsiccation,   19,  20. 
Factors    of   reactions,    proportions, 

102-104. 
Ferrated  albumin,  372-374. 

ammonium  chloride,  382. 
Ferric  acetate  solution,  368-370. 

acetate,  tincture,  371. 

ammonium  citrate,  392. 

ammonium  tartrate,  406. 

ammonium  sulphate,  445-446. 

benzoate,  375. 


648 


INDEX. 


Arsenic    compounds,    290-292,    374, 

526,  574,  575- 
compounds,     solubilities,     145, 

150. 

Arsenite,  potassium,  526. 
Atomic   weights,    tables,    635,    635- 

637. 
Balances,   181-182. 

hydrostatic,  155,  157. 
Barium  compounds,  292-298. 

compounds,  solubilities,  142. 
Basham's  mixture,  371. 
Baths,  189-191. 
Beakers,  no. 
Bellows,    184. 
Benzoate,  ammonium,  268. 

bismuth,  299. 

calcium,  318. 

ferric,  375. 

lithium,  464. 

mercuric,  488. 

potassium,  527. 

sodium,  575. 

Benzoates,  solubilities,  148, 149, 150. 
Bicarbonate,  ammonium,  269. 

potassium,  527. 

sodium,  576-577. 
Bismuth,  298. 
Bismuth  compounds,  299-314. 

compounds  solubilities,  145. 
Bisulphide,  carbon,  337. 
Bisulphite,   sodium,  578. 
Bitartrate,   potassium,  528. 

sodium,  578. 
Bleaching  powder,  342. 
Blower,   184. 
Blue-stone,  352. 
Boiling  points,  63,  72. 
Boiling  vessels,  66. 
Bone  phosphate,  328. 
Borate,  sodium,  606. 
Borates,  solubilities,  147. 
Borax,  606. 
Borax-tartar,  529. 
Borocitrate,  magnesium,  469. 

potassium,  539. 
Boroglycerin,  221. 
Borotartrate,  potassium,  530. 

potassium-sodium,  529. 
Bromate,  potassium,  530. 
Bromide,  ammonium,  270-271. 

barium,  293. 

calcium,  318. 

ferrous,  375. 

lithium,  465. 

mercuric,  489. 

potassium,  53I-533- 

sodium,  578-579. 

strontium,  609. 

zinc,  621. 


Bromides,  solubilities,  146,  149. 
Bromine,  200-202,  314,  315. 
Buchner  funnel,  47. 
Burner,  Erlenmeyer,  185. 
Burners,  183-186,  188. 
Burner  supports,  189. 
Buoyancy,  153,  154. 
Cadmium  compounds,  315-317. 

compounds,   solubilities,   143. 
Calcination,  21. 
Calcium  compounds,  317-334. 

compounds,     solubilities,     142- 

143. 
Calomel,  510-514. 

precipitated,  510-514. 
Calx,  327. 

sulphurata,  332. 
Carbon,  334. 

dioxide,  125,  335. 

disulphide,  337. 
Carbamate,  ammonium,  272. 
Carbonate,  ammonium,  272. 

barium,  293. 

cadmium,  315. 

calcium,  319. 

bismuthyl,  306-308. 

iron,  mass,  378. 

iron,  saccharated,  376. 

lead,  451. 

lithium,  465. 

magnesium,  469-470. 

manganese,  482. 

potassium,  533-535- 

sodium,  579-582. 

strontium,  609. 

zinc,  621-622. 
Carbonates,  action  on  acids,  121. 

solubilities,   147,  150. 
Carbonic  acid  gas,  335. 

acid  water,  335. 
Carlsbad  salt,  604,  605. 
Casseroles,  50. 
Centrifugator,  96. 
Cerite,  337. 
Cerium  compounds,  337-338. 

compounds,  solubilities,  143. 
Chalk,  prepared,  320. 
Charcoal,  animal,  334. 
Chemical  solution,  37,  117-118,  121, 

123,  124. 

Chloramide,  mercuric,  493. 
Chlorate,  potassium',  535. 

sodium,  582. 

Chlorates,  solubility,   146.   149,   150. 
Chloride,  aluminum,  257-258. 

ammonium,  274-276. 

antimony,  280-281. 

barium,  294. 

bismuthyl,  312. 

cadmium,  316. 


INDEX. 


649 


Chloride,  calcium,  320. 

copper,  349. 

ferric,  379-382. 

ferric,  solution,  382-387. 

ferric,  tincture,  387-390. 

ferrous,  390. 

gold,  356. 

gold  and  sodium,  357-358. 

lithium,  465. 

magnesium,  471-472. 

manganese,  484. 

mercuric,  489-491. 

mercurous,  510-514. 

of  lime,  342. 

potassium,  537. 

silver,  566. 

sodium,  583-584. 

strontium,    610. 

tin,  619. 

zinc,  622. 
Chlorides,  solubility,  145,   146,  149, 

150. 
Chlorine,  125,  338-341. 

water,  339-340. 
Chlorinated  lime,  342. 
Chloroplatinic  acid,  523. 
Chromate,  barium,  296. 

lead,  452. 

potassium,  544. 
Chrome  alum,  343. 
"Chromic  acid,"  344,  346. 

anhydride,  344. 
Chromium  compounds,  342-346. 

compounds,   solubilities,   144. 
Circulatory  displacement,  37. 
Citrate,  ammonium,  268. 

bismuth,  300. 

ferric,  39 1-393- 

ferric  solution,  393-396. 

ferric,  with  quinine,  396-400. 

ferric,  with  strychnine,  400. 

lithium,  466. 

magnesium,  472-475. 

potassium,  538. 

sodium,  solution,  584. 
Citrates,  solubilities,  148,  150. 
Citrine  ointment,  499. 
Clarification  of  liquids,  47-62. 
Cobalt  compounds,   solubility,   143. 
Co-efficients  of  solubility,  44. 
Colloids,  98. 

Combustion  of  metals,  21. 
Compounds,  true  chemical,  29. 
Condensers,  73-76. 
Condensing-watcr,  71-72. 
Copper  compounds,  347-354. 

compounds,  solubility,  144. 
Cork  borer,  75. 
Corrosive  sublimate.  489-491. 
Cream  of  tartar,  528. 


Crucibles,   17,  18. 
Crystal  meal,  78. 

water,   18-20,  85-87. 
Crystallization,  78-97. 
Crystallizers,  92,  96. 
Crystallography,  81-84. 
Crystalloids,  98. 
Cubes,  81,  85. 
Cyanate,  potassium,  540. 
Cyanide,   mercury,   493-496. 

potassium,  541. 

silver,  567. 

zinc,  624. 

Cyanides,  solubilities,  146,  149. 
Decantation,  48-50,  109,  HI. 

jar,   109. 

Decrepitation,  85. 
Dehydration,  18,  19. 
Deliquescence,  29,  96,  130,  134,  140. 
Densities  of  solids  and  liquids,  151- 

166. 

Dermatol,  308. 
Desiccation,  18,  19,  96. 
Desiccators,  96. 
Diachylon  plaster,  459. 
Dialysed  iron,  99,  403. 
Dialyser,  98. 
Dialysis,  98-99. 
Dichromate,  potassium,  542. 
Dioxide,  barium,  296. 

hydrogen,  359-363. 
Dissociation   of  salts   in   solutions, 

28-32. 

Distillation,  70-77. 
Disulphide,  carbon,  337. 
Donovan's  solution,  291. 
Drum  sieve,  14. 
Dry  oxidation,  21. 
Dry  processes,  4. 
Drying  closets,  19,  179. 
Efflorescence,   19,  87,  96,   130. 
Elixirs,   129. 
Elutriation,  13. 
Epsom  salt,  480. 
Erlcnmeyer  flasks,  no. 
Ethylate,  sodium,  586. 
Ethylsulphate,  sodium,  585. 
Evaporation,  63-69. 

dishes,  67. 
Exsiccation,   19,  20. 
Factors   of   reactions,    proportions, 

102-104. 
Ferrated  albumin,  372-374. 

ammonium  chloride,  382. 
Ferric  acetate  solution,  368-370. 

acetate,  tincture,  371. 

ammonium  citrate,  392. 

ammonium  tartrate,  406. 

ammonium  sulphate,  445-446. 

benzoate,  375. 


650 


INDEX. 


Ferric  chloride,  379-382. 

chloride,  solution,  382-387. 

chloride,  tincture,  387-390. 

chloride,  tinqture  ethereal,  390. 

citrate,  391-393- 

citrate,  solution,  393-396. 

citrate,  with  quinine,  396-400. 

citrate,  with  quinine,  solution, 
400. 

citrate,  with  strychnine,  401. 

ferrocyanide,  409. 

hydroxide,   410-413. 

hydroxide,  with  magnesia,  413. 

hypophosphite,  414. 

malate,  408. 

nitrate  solution,  401-402. 

oleate,  422. 

oxide,  423. 

oxide,  saccharated,  433. 

oxychloride  solution,  402. 

phosphate,   precipitated,   428. 

phosphate,   soluble,  429-430. 

potassium  tartrate,  407. 

pyrophosphate,        precipitated, 
431- 

pyrophosphate,     soluble,     431- 
433- 

subsulphate,  441. 

subsulphate  solution,  442. 

sulphate,  basic,  441. 

sulphate  solution,  443-445. 

tannate,  447. 

valerate,  447. 

Ferricyanide,  potassium,  544. 
Ferricyanides,  solubilities,  146. 
Ferrocyanide,  iron,  409. 

potassium,  545-546. 
Ferrocyanides,  solubilities,  146. 
Ferroso-ferric  oxide,  424-425. 

phosphate,  425-426. 
Ferrous  ammonium   sulphate,  441. 

arsenate,  374. 

bromide,  375. 

carbonate,  mass,  378. 

chloride,   390. 

iodide,  415. 

iodide  glycerite,  419. 

iodide  saccharated,  415. 

iodide  syrup,  416-419. 

lactate,  419-422. 

mono-meta-sulphate,  440. 

oxalate,  422. 

phosphate,  425. 

phosphate  syrup,  427. 

sulphate,  437-439- 

sulphate,  dried,  440. 

sulphide,  447. 
Filtration,  52-62. 
Fire  dangers,  202. 
Flames  of  burners,  186. 


Flasks,  graduated,  159,  161. 
Fletcher  burners,  183. 
Flores  martis,  382. 
Fowler's  solution,  526. 
Freezing  mixtures,  30-31. 
Fume  chamber,   180. 
Funnel,   Buchner,  47. 

cropped,  48. 

corrugated,  58. 

filter,  58. 

hot  water,  60. 

perforated,   58. 
Furnace,  Roessler,  187. 
Furniture,  laboratory,   179-180. 
Fusion,   16. 

aqueous,   18,   19,  87,   133. 
Gas  apparatus,  125,  126,  127. 
Gas  burners,  183-186,  188. 
Gas  operations,  117,  125. 
Gas  stoves,   183-184. 
Glass,  liquid  or  soluble,  603. 
Glauber's  salt,  603. 
Glycerin  as  a  solvent,  33. 
Glycerin  bath,  191. 
Glycerite,  boroglycerin,  222. 

ferrous  iodide,  419. 

lead  subacetate,  463. 

lead  tannate,  459. 
Gold,  355- 
Gold  chloride,  356. 

chloride,  with  sodium  chloride, 

357-358. 

Gold  compounds,  solubility,  145. 
Goulard's  extract,  461. 
Graduated  cylinders,   165. 

flasks,    159,    161. 
Graduates,   182,   183. 
Graduation  of  metals,  15. 
Granulation  of  salts,  90. 
Haller's  acid  drops,  247. 
Heat  in  evaporation,  68. 
Heat,  damaging  effects  of,  137-138. 
Heat  in  solution,  38-40. 
Heat,  steam,  191-192. 
Heating  apparatus,  182-194. 
Homoeomorphous    substances,    79. 
Hood,  180. 

Hot  air  chambers,  191. 
Hot  water  coil,  191. 
Hydrogen,  359. 

apparatus,  125. 

dioxide  solution,  359-363. 

peroxide  solution,  359-363. 

sulphide,  363. 

sulphide  apparatus,  125. 
Hydrometers,   161-166. 
Hydroxide,  aluminum,  258-260. 

barium,  298. 

bismuth,  302. 

calcium,  321. 


INDEX. 


651 


Hydroxide,  chromium,  346. 

ferric,  410-413. 

potassium,  546-549. 

potassium,  solution,  547-549- 

potassium,  solution,  table.  646. 

sodium,  586-588. 

sodium,  solution,  587-588. 

sodium,  solution,  table,  646. 

strontium,  611. 
Hydroxides,    metallic,    solubilities, 

145,  149- 
Hygroscopic  substances,  18,  19,  69, 

134,  140. 
Hypochlorite,  calcium,  342. 

sodium,  solution,  589. 
Hypophosphite,  calcium,  323-325. 

ferric,  414. 

potassium,  550. 

sodium. 
Hypophosphites,     solubilities,     147, 

149- 

syrup,  325. 

syrup,   with   iron,   325. 
"Hyposulphite  of  sodium,"  607. 
Hypothiosulphite,    potassium,    550- 

551. 

Ignition,   18,  21. 
Interstitial  water,  85. 
lodate,  potassium,  552. 
Iodide,  ammonium,  276. 

arsenous.  291. 

bismuthyl,   313. 

cadmium,  316. 

calcium,  326. 

ferrous,  415. 

ferrous,  saccharated,  415. 

ferrous,   syrup,  416-418. 

lead,  453. 

lithium,   467. 

manganese,  syrup,  484. 

mercury  green,  515. 

mercury  red,  496-497. 

mercury  yellow,  517. 

potassium,  552-556. 

silver,  567. 

sodium. 

•strontium,  611. 

sulphur,  618. 

zinc.  625. 

Iodides,  solubilities,  146.  149,  150. 
Iodine,  364. 
Iron  compounds,  368-447. 

compounds,  solubilities,  144. 
Iron  mortars,  10-11. 
Iron,  powdered,  366. 

reduced,  366-368. 

salts,  colors  of,  32. 

stands  for  retorts,  etc..  76-77. 
Isomorphous  substances.  79. 
Jewel  heater,  184. 


Kermes  mineral,  288. 
Kipp  apparatus,  125. 
Kissingen  salt,  584. 
Labarraque's   solution,  589. 
Laboratory  furniture,  179-180. 

journal,  203. 

rules  and  precautions,   197-205. 
Lactate,  calcium,  326. 

ferrous,  419-422. 

magnesium,  477. 

strontium,  612. 

zinc,  625. 

Lactates,  solubilities,  148,  149,  150. 
Lapis  divinus,  355. 

infernalis,   569. 
Latent  heat  of  vapor,  70,  71. 
Law  of  buoyancy,  153,  154. 
Lead  compounds,  448-464. 

compounds,  solubilities,  144. 
Leras'  solution,  433. 
Levigation.  13. 

Light,  damaging  effects  of,  135,  136. 
Lime,  327. 

chlorinated,  342. 

sulphurated,  332. 

syrup  of,  322. 

water,  322. 
Liquor  acidi  arsenosi,  290. 

acidus  Halleri,  247. 

ammonii  acetatis,  266-267. 

ammonii   hydroxidi,   263-265. 

arseni  et  hydrargy.ri  iodidi,  291. 

arsenicalis,  526. 

calcis,  322. 

ferri  acetatis,  368-370. 

ferri  albuminati,  372. 

ferri  albuminati  alkalinus,  373. 

ferri  chloridi,  382-387. 

ferri  citratis,  393-396. 

ferri  dialysati,  403. 

ferri  et  ammonii  acetatis,  371. 

ferri  et  mangani  peptonatus,405. 

ferri  et  quininae  citratis,  400. 

ferri  nitratis,  401-402. 

ferri  oxychloridi,  402. 

ferri  peptonati,  405. 

ferri  subsulphatis,  442. 

ferri  sulphatis,  443-445. 

ferri  tersulphatis.  443-445. 

hydrargyri  nitratis,  498. 

hydrargyri  peptonati,  505. 

hydrogenii  dioxidi,  359-363. 

iodi  compositus,   364-. 

magnesii  citratis.  475. 

plumbi  subacetatis,  461-463. 

plumbi  snbnci-tHtis  d;luius.  464. 

potassao,    547-549- 

potassii   arsenitis.  526. 

potassii  citratis,  538. 

sodae,  587-588. 


652 


INDEX. 


Liquor  sodae  chloratae,  589. 

sodii  arsenatis,  575. 

sodii  citratis,  584. 

spdii  silicatis,  603. 

zinci  chloridi,  623-624. 
Litharge,  457. 
Lithium  compounds,  464-467. 

compounds,   solubilities,   142. 
Litmus  paper,  122. 
Liver  of  sulphur,  550,  551. 
Lixiviation,  25. 
Lunar  caustic,  569. 
Lysimeter,  Dr.  Rice's,  42-44. 
Magmas,  112. 
Magnesium  compounds,  468-482. 

compounds,  solubilities,  143. 
Malate,  iron,  408. 
Manganese  compounds,  482-486. 

compounds,  solubility,  144. 

peptonate  with  iron,  405. 
Mass,  153. 
Massicot,  457. 
Materials,  4,  5,  7,  8,  101. 
Measures,  graduated,  165,  182,  183. 
Mendeleeff  on  solutions,  28-30. 
Mercurius     solubilis    Hahnemanni, 

SIS- 

Mercury,  487. 
Mercury  compounds,  487-521. 

compounds,  solubility,  144. 
Metals,  action  of,  on  acids,  119. 
Metathesis,  7,-  101. 
Microcosmic  salt,  600. 
Micro-crystalline  substances,  78. 
Mills,  10. 
Minium,  457. 

Mixtures,  percentage,  167-178. 
Molecular  combinations,  29,  30. 
Monsel's   powder,   441. 

solution,  442. 
Mortars,  iron,  10-11. 

porcelain,    12,    13,  37. 
Mother-liquor,  93,  no,  in. 
Neutralization,  5,  118,  122. 
Nickel  compounds,  solubility,  143. 
Nitrate,  ammonium,  277. 

barium,  297. 

bismuth,  303. 

bismuthyl,  308-312. 

cadmium,  317. 

cerium,  337. 

copper,  349. 

lead,  455. 

iron,  solution,  401. 

mercuric,  498. 

mercurous,  519. 

mercury  ointment,  499. 

potassium,   556-558. 

silver,  568-570. 

sodium,  591-592. 


Nitrate,  strontium,  612. 
Nitrates,  solubility,   149,  150. 
Nitrite,  sodium,  592. 
Nitrites,  action  of  on  acids,  121. 

solubility,  147. 
Nitroprusside,  sodium,  592. 
Oleate,  aluminum,  260-261. 

bismuth,  304. 

copper,  350. 

ferric,  422. 

lead,  456. 

mercury,  500. 

potassium,  558. 

silver,  571. 

zinc,  625-627. 
Oleates,  solubilities,  148. 
Ostwald  on  solutions,  31. 
Ovens,   copper,    191-192. 
Oxalate,  ammonium,  278. 

cerium,  337. 

ferrous,  422. 

potassium,  559. 
Oxalates,  solubilities,  148. 
Oxidation  and  reduction,  7,  21,  117, 

124. 
Oxide,  antimony,  282-284. 

arsenous,  292. 

barium,  298. 

bismuth,  304. 

calcium,  327. 

cerium,  338. 

copper,  351. 

ferric,  423. 

ferric  saccharatedj  433. 

ferroso-ferric,  424. 

lead,  457- 

magnesium,  477-479. 

manganese,  483. 

mercury,  black,  520. 

mercury,  red,  501. 

mercury,  yellow,  503-505. 

silver,  571. 

strontium,  613.   . 

zinc,  628. 

Oxides,  solubilities,  145. 
Oxidizing  agents,  124-125. 
Oxychloride,  antimony,  284. 

bismuth,  312. 

ferric,  solution,  402. 
Oxygen,  preparation,  125,  184/521. 
Oxy-iodide,  bismuth,  313. 
Paraffin  bath,  191. 
Pearl  ash,  533. 
Peptonated  iron,  404,  405. 

mercury,    505. 
Percentage  solutions  and  mixtures. 

168-178. 

Permanganate,  potassium,  568. 
Peroxide,  hydrogen,  359-363. 

lead,  458. 


INDEX. 


653 


Phenolsulphonate,  sodium,  595. 

zinc,  628. 
Phosphate,  ammonium,  279. 

calcium,  328-330. 

ferric,  428-430. 

ferroso-ferric,  425-426. 

ferrous,   syrup,  427. 

lithium,  467. 

manganese,  485. 

potassium,  561. 

sodium,  595-599. 

sodium  ammonium,  600. 
Phosphates,  solubilities,  147,  150. 
Phosphorated  oil,  522. 
Phosphorus,   202,   522. 
Physical  precipitation,  36,  97,   100. 
Pipettes,  50. 
Plaster,  lead,  459. 
Platinum  chloride,  523. 

cone  for  filters,  58. 
Potash,  533. 
Potassa,  546. 

sulphurated,  550-551. 

with  lime,  549. 
Potassium  compounds,  524-564. 

compounds,  solubilities,  141. 
Potio  Riveri,  585. 
Powdering,   10-14,   115. 
Precipitation,  100-116. 

physical,  36,  97,  100. 
Prepared  chalk,  320. 
Preservation  of  chemical  products, 

I.33-I40. 
Presses,  54-50. 
Prisms,  82,  83,  85. 
Processes,  dry  and  wet,  3-5. 
Products,  3-8. 

damaged,  how  treated,  128. 

preservation  of,  133-140. 

unfinished,  uses  of,  128. 
Prussian  blue,  409. 
Prussiate    of    potash,    yellow,    545- 
546. 

of  potash,  red,  544. 
Purification  of  chemicals,  116,  128, 

130. 

Pycnometers,  158,  159,  160. 
Pyrophosphate,  ferric,  431-433. 

sodium,  600. 
Pyrophosphates,     solubilities,     147, 

ISO. 

Pyramidal  crystals,  85. 
Reaction  on  test  paper,  122. 
Reactions,  chemical,  kinds,  7. 

prognosis  of,  7. 
Receivers,  73. 
Red  lead,  457. 
Reduced  iron,  366-368. 
Retort,  iron,  184. 

stands,  76,  77. 


Retorts,  glass,  73,  74. 
Rhodankalium,  562,  563. 
Rice's  lysimeter,  42-44. 
''Riders"  on  balances,  156,  157. 
Roasting  of  sulphides,  21. 
Rochelle  salt,  561-562. 
Roessler  furnace,    187. 
Rubber  stoppers,  perforated,  75. 
Rules    for    adjusting    and    finding 
strength    of    solutions    and 
mixtures,  167-178. 
Saccharated  iron,  soluble,  433. 
Safety  tubes,  75. 
Sal  sodae,  579~58o. 
Salicylate,  bismuth,  305. 

lithium,  467. 

mercury,  506. 

potassium,  561. 

sodium,  601. 

zinc,  629. 

Salicylates,  solubilities,    148,   149. 
Salt,  common,  583-584. 

Carlsbad,  604. 

Kissingen,  584. 

microcosmic,  600. 

Vichy,  577. 

Salt  solutions,  chemical  nature  of, 
28-32. 

solutions,  colors  of,  31-32. 
Salts  of  tartar,  533. 
Sand-baths,  189,  190. 
Santoninate,  sodium,  602,  603. 
Sapo  durus,  593-594- 

mollis,  558. 
Saturation,  118,  123. 
Scale  salts,  128,  150. 
Schlippe's  salt,  286. 
Sieves,  14. 

Silicate,  sodium,  solution,  603. 
Silver  compounds,  565-572. 

compounds,  solubilities,  145. 
Soaps,  558,  593-594- 
Soda,  586. 
Soda  water,  336. 
Sodium  compounds,  572-609. 

compounds,  solubilities,  142. 
Solubilities    of    chemical  products, 
141-150. 

of  chemical  products,  summary. 

148. 

Solubility,  33-35,  41-45. 
Solution,   24-46. 

chemical,  117,  121. 

chemically  considered,   30-32. 

Leras',   433. 
Solution-baths,  191. 
Solutions,   Mendeleeff  on,  28. 

Ostwald  on,  31. 

strength  of,  45-46,  167-178. 
Solvents,  28. 


654 


INDEX. 


Spatulas,  steel,  12,   13. 
Specific   gravity,    151-153. 

gravity,    instruments,    155-156- 

volume,  166. 
Spirit  lamps,  187-188. 
Spirit  of  ammonia,  265. 

of  ammonia,  aromatic,  266. 

of  Mindererus,  266-267. 
Spritz  bottles,    113. 
Steam  heat,  191-192. 
Stirrers,  68. 
Stoves,  gas,  183,  184. 
Strainers,  51-54,  112. 
Strontium  compounds,  609-613. 

compounds,  solubilities,  142. 
Subacetate,  lead,  glycerite,  463. 

lead,  solution,  461. 
Subcarbonate,  bismuth,  306-308. 

copper,  351. 

iron,  435. 

Subgallate,  bismuth,  308. 
Sublimation,  21-23. 
Subnitrate,  bismuth,  308-312. 
Subsulphate,  ferric,  441. 

ferric,  solution,  442. 

mercury,  508. 
Sugar  of  lead,  448-451.- 
Sulphate,  ammonium,  279. 

aluminum,  261-262. 

cadmium,  317. 

calcium,  331. 

cerium,  338. 

chromium,  346. 

copper,  351-353- 

copper,  ammoniacal,  354. 

copper  and  potassium,  354. 

ferric,  basic,  441. 

ferric,  normal,  443-445. 

ferrous,  437-439- 

ferrous,  dried,  440. 

iron    and    ammonium    (ferric), 
445-446. 

iron  and  ammonium  (ferrous), 
441. 

magnesium,  480. 

manganese,  486. 

mercury,  507-508. 
Sulphate,  potassium,  563. 

sodium,  603-605. 

zinc,  629-631. 

Sulphates,  solubilities,  147,  149,  150. 
Sulphethylate,    sodium,    585. 
Sulphide,  antimony,  285-290. 

calcium,  332. 

ferrous,  447. 

hydrogen,  363. 

mercury,  509-510. 
Sulphides,  action  of,  on  acids,  121. 

solubilities,  146. 
Sulphite,  calcium,  333.- 


Sulphite,  magnesium,  482. 

potassium,  563. 

sodium,  605. 

zinc,  631. 
Sulphites,  action  of,  on  acids,  121. 

solubilities,  147. 
Sulphocarbolate,  sodium,  595. 

zinc,  628. 

Sulphocyanate,    potassium,  562-563. 
Sulphovinate,    sodium,   585. 
Sulphurated  lime,  332. 

lime,  solution,  334. 

potassa,  550,  551. 
Sulphur,  613-616. 

dioxide,  616,  617. 

iodide,  618. 

precipitated,  614-616. 

washed,  613. 
Syphons,  50-52. 
Syrup,  ferrous  bromide,  375. 

ferrous   iodide,  415-418. 

ferrous  phosphate,  427. 

hydriodic  acid,  224. 

hypophosphites,  325. 

hypophosphites,  with  iron,  325. 

iron,    quinine     and     strychnine 
phosphates,  430. 

iron,  saccharated,  435. 

lime,   323. 

manganese  iodide,  484. 

phosphates     of     iron,     quinine 

and  strychnine,  430. 
T-tubes,  74. 
Table  of  acetic  acid,  639. 

ammonia  water,  645. 

atomic  weights,  635. 

atomic  weights,  multiples,  636, 
637. 

of  hydrobromic  acid,  640. 

hydrochloric  acid,  640. 

nitric  acid,  641-642. 

phosphoric    acid,    642. 

potassium   hydroxide  solution, 
646. 

sodium  hydroxide  solution,  646. 

solubilities,  141-150. 

sulphuric  acid,  643-644. 

thermometric   equivalents,  638. 

weights  and  measures,  211. 
Tannate,  bismuth,  314. 

iron,  447. 

lead,  459. 

mercury,  521. 
Tartar,  528. 

emetic,  284. 

Tartarus  boraxatus,  529. 
Tartrate,  antimonyl-pocassium,  284. 

iron  and  ammonium,  406. 

iron  and  potassium,  407. 

magnesium,  482. 


INDEX. 


655 


Tartrate,  potassium,  564. 

potassium-sodium,  561-562. 

sodium,  606. 

Tartrates,  solubilities,  148,  150. 
Tenaculum,  53. 
Tersulphate,  iron,  443-445. 
Test-paper,  122-123. 
Thermometers,  laboratory,  72-73. 
Thermometric     equivalents,     table, 

638. 

Thiocyanate,  potassium,  562-563. 
Thiosulphate,  sodium,  607. 
Thistle-tube,  75. 
Tin  chloride,  619. 
Tincture  of  iodine,  364. 

of  iodine,  decolorized,  365-366. 

of  iron  acetate,  371. 

of  iron  chloride,  387-390. 
Tripods,  189. 
Trituration,  12,  16. 
Tube  fittings,  74,  75. 
Turbidation,  89. 
Turpeth,  mineral,  508. 
Valcrate.  ammonium,  280. 

ferric,  447. 

sodium,  608. 


Valerate,  zinc. 

Valerates,  solubilities,  148,  149,  150. 

Vapor,  latent  heat  of,  70-71. 

Vaporization,  64. 

Vermilion,  509. 

Vichy  salt,  577. 

Vlemingkx's   solution,    334. 

Water,  212-214. 

as  a  solvent,  33. 

crystallization,    19,    20,    28,    29, 
85-87- 

interstitial,  85. 
Water-baths,   189-190. 
Water-glass,  603. 
Wash-bottles,  126,  127. 
Weights  and  measures,  211. 
Wet  oxidation,   117,  124. 

processes,  5. 
White  lead,  451. 

precipitate,  492. 
Wire  cloth,  uses  of,  188. 
Witherite,  295. 
Woulff  bottles,  126,  127. 
Zinc  compounds,  619-632. 

compounds,  solubilities,   143. 


old-berg.  0-    _.  general, , 


